Magnetic memory devices and methods of operating the same

This application claims the benefit of priority under 35 U.S.C. §119 from Korean Patent Application No. 10-2012-0066983, filed on Jun. 21, 2012, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.

1. Field

Example embodiments relate to magnetic memory devices and methods of operating the same.

2. Description of the Related Art

Magnetic random access memories (MRAMs) are memory devices that store data by using a variation in resistance of a magnetic tunneling junction (MTJ) element. The resistance of the MTJ element varies according to a magnetization direction of a free layer. That is, when the magnetization direction of the free layer is the same as a magnetization direction of a pinned layer, the MTJ element has low resistance. When the magnetization direction of the free layer is opposite to the magnetization direction of the pinned layer, the MTJ element has high resistance. A case where the MTJ element has the low resistance may correspond to data ‘0’, and a case where the MTJ element has the high resistance may correspond to data ‘1’. Because MRAMs are non-volatile, capable of high speed operations and have high endurance, MRAMs have gained attention as one of the next generation non-volatile memory devices.

A typical MRAM includes an MTJ element having a horizontal magnetization, and uses a digit line and a bit line to switch a magnetization direction of a free layer. Such an MRAM uses an MTJ element having a horizontal magnetization, and also has a relatively complicated structure, and accordingly, it is difficult to realize high-densification.

In the case of a spin transfer torque magnetic random access memory (STT-MRAM) that does not use a digit line, a magnetization direction of a free layer is switched by using a spin torque that occurs due to a current flowing through an MTJ element. However, to secure data retention characteristics of a free layer, a material with high magnetic anisotropy energy is used as a free layer material. When a material having a high magnetic anisotropy is used for the free layer material, an amount of the current (that is, a switching current) required to switch a magnetization direction of the free layer increases. Accordingly, a large-size cell transistor is required for supplying the switching current. In addition, in the case of the STT-MRAM, a writing current needs to be repeatedly provided to the MTJ element. Accordingly, problems related to endurance and reliability of a tunneling layer interposed between a free layer and a pinned layer of an MTJ element may occur.

Example embodiments relate to magnetic memory devices and methods of operating the same.

Provided are magnetic memory devices having high-density (high integration) and high performance.

Provided are magnetic memory devices having improved endurance and reliability.

Provided are magnetic memory devices capable of suppressing or preventing writing error and cross talk.

According to example embodiments, a magnetic memory device includes a magnetoresistive element including a free layer, a pinned layer, and a separation layer between the free layer and the pinned layer; a first conductive line connected to the free layer and configured to apply a Rashba field to the free layer; and a second conductive line spaced apart from the free layer and configured to apply an external magnetic field to the free layer, wherein a magnetization direction of the free layer is switchable by application of the Rashba field and the external magnetic field to the free layer.

The free layer and the pinned layer may have perpendicular magnetic anisotropy.

The magnetic memory device may be configured to apply a first current to the first conductive line to induce the Rashba field, and the second conductive line may be configured to apply the external magnetic field to the free layer in a direction identical to a direction of the first current.

The first conductive line may be configured to apply the Rashba field to the free layer in a first direction, and the second conductive line may be configured to apply the external magnetic field to the free layer in a second direction which is perpendicular to the first direction.

The magnetoresistive element may have a bottom-pinned structure in which the pinned layer is under the free layer, the first conductive line may be on an upper surface of the magnetoresistive element, and the second conductive line may be under the magnetoresistive element.

The magnetoresistive element may have a top-pinned structure in which the pinned layer is above the free layer, the first conductive line may be on a lower surface of the magnetoresistive element, and the second conductive line may be under the first conductive line.

The first conductive line may be a bit line, and the second conductive line may be a word line.

The first conductive line and the second conductive line may cross each other, and the magnetoresistive element may be at an intersection point of the first conductive line and the second conductive line.

The magnetic memory device may further include a switching device connected to the magnetoresistive element.

The second conductive line may be a part of the switching device.

The switching device may include a transistor, and the second conductive line may be a gate line of the transistor.

The transistor may include a drain connected to the pinned layer.

The switching device may include a first transistor and a second transistor, a first magnetoresistive element is on the first transistor, and a second magnetoresistive element is on the second transistor. The first conductive line may be commonly connected to the first and second magnetoresistive elements.

The first transistor may include a first gate line, and the second transistor may include a second gate line, wherein each of the first and second gate lines corresponds to the second conductive line.

The first magnetoresistive element may be on the first gate line, the second magnetoresistive element may be on the second gate line, and the first conductive line may be on the first and second magnetoresistive elements.

The first magnetoresistive element may be on the first gate line, the second magnetoresistive element may be on the second gate line, and the first conductive line may be interposed between the first and second gate lines and the first and second magnetoresistive elements.

The first and second transistors may be both connected to a single source.

The magnetic memory device may further include a magnetic field focusing element configured to focus the external magnetic field on the magnetoresistive element.

The magnetic field focusing element may include a cladding layer on side walls of the second conductive line.

The cladding layer may include a magnetic material containing at least one of Ni, Co, and Fe.

According to example embodiments, a magnetic memory device includes a transistor including a source, a drain, and a gate; a magnetoresistive element that is connected to the transistor and includes a free layer, a pinned layer, and a separation layer interposed between the free layer and the pinned layer; and a bit line connected to the magnetoresistive element, wherein the bit line is configured to induce a Rashba field in the free layer, the gate is configured to apply an external magnetic field to the free layer, and a magnetization direction of the free layer is switchable by the Rashba field and the external magnetic field.

The bit line may be connected to the free layer.

The drain may be connected to the pinned layer.

The magnetoresistive element may be above the gate.

The gate may have a line shape crossing the bit line, and the magnetoresistive element may be at an intersection point of the gate and the bit line.

The magnetoresistive element may have a bottom-pinned structure in which the pinned layer is under the free layer, the bit line may be on an upper surface of the magnetoresistive element, and the gate may be under the magnetoresistive element.

The magnetoresistive element may have a top-pinned structure in which the pinned layer is above the free layer, the bit line may be on a lower surface of the magnetoresistive element, and the gate may be under the bit line.

The free layer and the pinned layer may have perpendicular magnetic anisotropy.

According to other example embodiments, a method of operating a magnetic memory device including a magnetoresistive element including a free layer, a pinned layer and a separation layer therebetween, a first conductive line connected to the free layer, and a second conductive line spaced apart from the free layer, includes writing data on the magnetoresistive element, wherein the writing of data includes applying a Rashba field to the free layer by providing a first current to the first conductive line; and applying an external magnetic field to the free layer by providing a second current to the second conductive line.

The free layer and the pinned layer may have perpendicular magnetic anisotropy.

The free layer may have a magnetization direction extending in a first direction, prior to applying the Rashba field and the external magnetic field, and the magnetization direction of the free layer may be switched to extend in a second direction by applying the Rashba field and the external magnetic field, and one of the first direction and the second direction is an upward direction, and the other one of the first direction and the second direction is an downward direction.

The external magnetic field may be applied to the free layer in a direction that is identical to a direction of the first current.

The Rashba field may be applied to the free layer in a first direction, and the external magnetic field may be applied to the free layer in a second direction perpendicular to the first direction.

The method may further include applying a second Rashba field to the free layer by providing a third current to the first conductive line, the third current having a direction opposite to that of the first current; and applying a second external magnetic field to the free layer by providing a fourth current to the second conductive line, the fourth current having a direction opposite to that of the second current.

The magnetic memory device may further include a switching device connected to the magnetoresistive element, and the second conductive line may be a part of the switching device.

The switching device may include a transistor, and the second conductive line may be a gate line of the transistor.

Example embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. FIGS. 1-10 represent non-limiting, example embodiments as described herein.

FIGS. 1 through 4 are perspective views of magnetic memory devices according to example embodiments;

FIGS. 5 through 8 are perspective views illustrating overall detailed structures of the magnetic memory devices of FIGS. 1 through 4 , according to example embodiments;

FIGS. 9A through 9D are perspective views for explaining a data writing method of a magnetic memory device according to example embodiments; and

FIG. 10 is a perspective view for explaining a data read method of a magnetic memory device according to example embodiments.

Various example embodiments will now be described more fully with reference to the accompanying drawings in which some example embodiments are shown. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments, and thus may be embodied in many alternate forms and should not be construed as limited to only example embodiments set forth herein. Therefore, it should be understood that there is no intent to limit example embodiments to the particular forms disclosed, but on the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.

In the drawings, the thicknesses of layers and regions may be exaggerated for clarity, and like numbers refer to like elements throughout the description of the figures.

Although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

It will be understood that, if an element is referred to as being “connected” or “coupled” to another element, it can be directly connected, or coupled, to the other element or intervening elements may be present. In contrast, if an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.).

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” if used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.

Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,” “upper” and the like) may be used herein for ease of description to describe one element or a relationship between a feature and another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, for example, the term “below” can encompass both an orientation that is above, as well as, below. The device may be otherwise oriented (rotated 90 degrees or viewed or referenced at other orientations) and the spatially relative descriptors used herein should be interpreted accordingly.

Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures). As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, may be expected. Thus, example embodiments should not be construed as limited to the particular shapes of regions illustrated herein but may include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle may have rounded or curved features and/or a gradient (e.g., of implant concentration) at its edges rather than an abrupt change from an implanted region to a non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation may take place. Thus, the regions illustrated in the figures are schematic in nature and their shapes do not necessarily illustrate the actual shape of a region of a device and do not limit the scope.

It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Example embodiments relate to magnetic memory devices and methods of operating the same.

FIG. 1 is a perspective view of a magnetic memory device according to example embodiments.

Referring to FIG. 1 , a magnetoresistive element MR 1 may be provided. The magnetoresistive element MR 1 may include a free layer FL 1 , a pinned layer PL 1 , and a separation layer SL 1 between the free layer FL 1 and the pinned layer PL 1 . The free layer FL 1 may be a magnetic layer having a variable (changeable) magnetization direction, and may be formed of a ferromagnetic material. The ferromagnetic material may include at least one of Co, Fe, and Ni, and may further include at least one other element, for example, B, Cr, Pt, Pd, or the like. The pinned layer PL 1 may be a magnetic having a fixed magnetization direction, and may be formed of a ferromagnetic material including at least one of Co, Fe, and Ni, for example. The ferromagnetic material may further include at least one other element, for example, B, Cr, Pt, Pd, or the like, in addition to Co, Fe, and Ni. The free layer FL 1 and the pinned layer PL 1 may be formed of different, or identical, materials. The free layer FL 1 and the pinned layer PL 1 may each have perpendicular magnetic anisotropy. In this case, the free layer FL 1 and/or the pinned layer PL 1 may include a Co-based material, and may include a single-layered or a multi-layered structure. For example, the free layer FL 1 and/or the pinned layer PL 1 may include at least one selected from the group consisting of Co, CoFe, CoFeB, CoCr, and CoCrPt, or may have a [Co/Pd] n structure, a [Co/Ni] n structure, or a [Co/Pt] n structure. In the [Co/Pd] n structure, n refers to the repeating number of the stack of Co and Pd, wherein Co and Pd are alternately stacked. N of [Co/Ni] n and [Co/Pt] n is the same as described above. The materials for forming the free layer FL 1 and the pinned layer PL 1 are merely examples, and, various other materials may also be used to form the free layer FL 1 and the pinned layer PL 1 . The separation layer SL 1 may be formed of an insulating material. For example, the separation layer SL 1 may include an insulating oxide, such as an Mg oxide and an Al oxide. When these materials, in particular, the Mg oxide, is used to form the separation layer SL 1 , a magnetoresistance ratio (that is, MR ratio) may increase. A thickness of the separation layer SL 1 may be about 5 nm or less, for example, about 3 nm or less. In the present example embodiments, the separation layer SL 1 and the free layer FL 1 may be sequentially stacked on the pinned layer PL 1 . That is, in the present example embodiments, the magnetoresistive element MR 1 has a bottom pinned structure wherein the pinned layer PL 1 is disposed under the free layer FL 1 .

A first conductive line W 1 for inducing a Rashba field F RB in the free layer FL 1 may be provided. The first conductive line W 1 may be connected to the free layer FL 1 . The first conductive line W 1 may be disposed on the free layer FL 1 and may contact the free layer FL 1 . The first conductive line W 1 may extend in a predetermined (or, alternatively, selected) direction, for example, an X-axis direction. The first conductive line W 1 may be formed of a metal that has strong spin orbit coupling, and an example of such a metal is Pt and/or Pd. A top surface of the free layer FL 1 contacts the first conductive line W 1 , and a bottom surface of the free layer FL 1 contacts the separation layer SL 1 . The first conductive line W 1 may be formed of a metal that has strong spin orbit coupling, and the separation layer SL 1 may be formed of an insulating material. Accordingly, an interfacial state between the free layer FL 1 and the first conductive line W 1 may be different from an interfacial state between the free layer FL 1 and the separation layer SL 1 . In this case, due to a current (hereinafter referred to as a first current I 1 ) flowing through the first conductive line W 1 , a Rashba field F RB may be applied to the free layer FL 1 . In more detail, when the first current I 1 is supplied to the first conductive line W 1 , due to an asymmetric electronic structure between a first interface of the free layer FL 1 with the separation layer SL 1 and a second interface of the free layer FL 1 with the first conductive line W 1 , an effective electric field may occur between the first interface and the second interface. The electric field causes an effective magnetic field in the free layer FL 1 . This magnetic field is the Rashba field F RB . The Rashba field F RB may be applied in a direction perpendicular to a direction of the first current I 1 . When the first current I 1 is applied in a reverse X-axis direction, the Rashba field F RB may be applied in a Y-axis direction. The Rashba field F RB effectively operates only inside the free layer FL 1 , and may hardly affect the outside of the free layer FL 1 .

A second conductive line W 2 for applying an external magnetic field F EX to the free layer FL 1 may be provided. In this regard, the terminology “external magnetic field” means a field applied from outside the free layer FL 1 to the free layer FL 1 (or, alternatively, the terminology “external magnetic field” means a field applied without providing, or supplying, a direct current through the magnetoresistive element MR 1 ). The second conductive line W 2 for generating the external magnetic field F EX may be spaced apart from the magnetoresistive element MR 1 . For example, the second conductive line W 2 may be spaced apart from the pinned layer PL 1 under the pinned layer PL 1 . The second conductive line W 2 may extend in a selected direction, for example, the Y-axis direction. Accordingly, the second conductive line W 2 may be disposed to cross the first conductive line W 1 . The magnetoresistive element MR 1 may be located at a point of intersection where the second conductive line W 2 crosses the first conductive line W 1 . When a current (hereinafter referred to as “a second current I 2 ”) is applied to the second conductive line W 2 , the external magnetic field F EX may occur from the second conductive line W 2 . The external magnetic field F EX may be applied to the free layer FL 1 . When the second current I 2 is applied in the Y-axis direction, the external magnetic field F EX in the free layer FL 1 may have a reverse X-axis direction or a direction similar thereto. A direction of the external magnetic field F EX in the free layer FL 1 may be perpendicular to the direction of the Rashba field F RB , or may be substantially similar to the perpendicular direction. In addition, the direction of the external magnetic field F EX applied to the free layer FL 1 may be identical, or similar, to the direction of the first current I 1 applied to the first conductive line W 1 to induce the Rashba field F RB .

A magnetization direction of the free layer FL 1 may be switched by the Rashba field F RB and the external magnetic field F EX . Due to the Rashba field F RB and the external magnetic field F EX which are perpendicular to each other, the magnetization (that is, a magnetic moment) of the free layer FL 1 may be perturbed, and the axis of magnetization (that is, magnetic moment) may rotate on a particular orbital. The rotating of the axis of the magnetization (that is, magnetic moment) on a particular orbital is referred to as a precession. While the precession of the magnetization of the free layer FL 1 , the direction of magnetization may be switched to (or, alternatively, in) a perpendicular direction. If the free layer FL 1 is magnetized in a Z-axis direction, due to the Rashba field F RB and the external magnetic field F EX , the magnetization direction of the free layer FL 1 may be switched to a reverse Z-axis direction.

The directions of the Rashba field F RB and the external magnetic field F EX illustrated in FIG. 1 are examples, and may vary. According to the direction of the first current I 1 , the direction of the Rashba field F RB may vary, and according to the direction of the second current I 2 , the direction of the external magnetic field F EX may vary. When the first current I 1 is applied in the X-axis direction, the Rashba field F RB may occur in a reverse Y-axis direction. When the second current I 2 is applied in the reverse Y-axis direction, the external magnetic field F EX may be applied in the X-axis direction or in a direction similar thereto. As such, when the directions of the Rashba field F RB and the external magnetic field F EX are opposite to those illustrated in FIG. 1 , the magnetization of the free layer FL 1 may be switched from a reverse Z-axis direction to a Z-axis direction. As described above, in the present example embodiments, the magnetization of the free layer FL 1 may be switched to (or, alternatively, in) a perpendicular direction by using the Rashba field F RB and the external magnetic field F EX .

In a typical STT-MRAM, a magnetization direction of a free layer is switched by using a current flowing through a magnetoresistive element (that is, an MTJ element). Accordingly, a separation layer (that is, a tunneling layer) of the magnetoresistive element (that is, MTJ element) needs to have very high endurance. Also, because ranges of a writing voltage (that is, a switching voltage) and a read voltage need to be determined within a voltage range in which the separation layer (that is, a tunneling layer) is not broken down, there are many limitations to set a range of an operation voltage (i.e., writing voltage and read voltage). When a distribution (range) of the writing voltage and a distribution (range) of the read voltage are close to a distribution (range) of a breakdown voltage of the separation layer (tunneling layer), an operation error, such as a writing error, and reliability related problems may occur. To suppress these problems, the distribution (range) of the writing voltage, the distribution (range) of the read voltage, and the distribution (range) of the breakdown voltage need to be strictly managed (controlled). These problems may make commercialization of STT-MRAM difficult.

However, in the present example embodiments, a current does not flow through the magnetoresistive element MR 1 , and the first and second currents I 1 and I 2 are applied to only the first and second conductive lines W 1 and W 2 to switch a magnetization direction of the free layer FL 1 . That is, in the present example embodiments, a current for switching the magnetization direction of the free layer FL 1 , that is, the first and second currents I 1 and I 2 do not flow through the magnetoresistive element MR 1 . Accordingly, in the present embodiment, any damage to the separation layer SL 1 (that is, a tunneling layer) of the magnetoresistive element MR 1 by a switching current (that is, a writing current) or deterioration of characteristics of the separation layer SL 1 may be prevented. Accordingly, endurance requirement conditions with respect to the separation layer SL 1 (that is, a tunneling layer) may be relieved, and deterioration of characteristics of the magnetoresistive element MR 1 by the writing current may be prevented. In addition, although a read current may be applied to flow through the magnetoresistive element MR 1 , the intensity (magnitude) of the read current is much lower than that of the writing current of a typical STT-MRAM, the damage to the separation layer SL 1 (that is, a tunneling layer) by the read current or deterioration of the separation layer SL 1 by the read current may not occur. Also, in the present embodiment, since the writing current does not flow through the magnetoresistive element MR 1 , there is no need to consider a distribution (range) of a writing voltage with respect to the magnetoresistive element MR 1 . That is, regarding the magnetoresistive element MR 1 , only the distribution (range) of a read voltage and the distribution (range) of a breakdown voltage may be taken into consideration. Accordingly, requirements for the management of the operation voltage are relieved, and a range of the operation voltage may be freely set, and the possibility of occurrence of an operation error may be lowered. Thus, a device structure according to example embodiments may be advantageous for commercialization of an MRAM.

Additionally, in the case of a typical MRAM in which a magnetization direction of a free layer is switched by using a digit line and a bit line, the use of an MTJ element having a horizontal magnetization and a complicated structure make it difficult to realize high-densification. In addition, in the typical MRAM, even a cell adjacent to a target cell that is to be switched may be switched or half-switched. This phenomenon is referred to as a cross talk. However, in the case of a magnetic memory device according to example embodiments, a magnetoresistive element MR 1 having a perpendicular magnetization is used and also, the magnetic memory device has a more simplified structure than the typical MRAM. Thus, the magnetic memory device according to example embodiments is suitable for high densification and high integration. Also, in a magnetic memory device according to example embodiments, the Rashba field F RB affects only inside the free layer FL 1 , and does not affect outside the free layer FL 1 . Accordingly, the cross talk may be prevented or suppressed.

The structure illustrated in FIG. 1 may be variously modified. For example, the structure of FIG. 1 may be modified to the structure of FIG. 2 .

Referring to FIG. 2 , a magnetoresistive element MR 1 ′ may have a top-pinned structure in which the pinned layer PL 1 is located above the free layer FL 1 . That is, the magnetoresistive element MR 1 ′ may include the separation layer SL 1 and the pinned layer PL 1 which are sequentially stacked on the free layer FL 1 in this stated order. In this case, the first conductive line W 1 may contact a lower surface of the magnetoresistive element MR 1 ′, that is, a lower surface of the free layer FL 1 . The second conductive line W 2 may be spaced apart from the first conductive line W 1 under the first conductive line W 1 . The first conductive line W 1 and the second conductive line W 2 may cross each other. The magnetoresistive element MR 1 ′ may be located at a point of intersection where the first conductive line W 1 and the second conductive line W 2 cross each other. In this regard, although the magnetoresistive element MR 1 ′ is not located between the first conductive line W 1 and the second conductive line W 2 , the magnetoresistive element MR 1 ′ is provided to be located to correspond to the intersection point of the first conductive line W 1 and the second conductive line W 2 .

Even in the structure of FIG. 2 , the magnetization direction of the free layer FL 1 may be switched by the Rashba field F RB generated by the first conductive line W 1 and the external magnetic field F EX generated by the second conductive line W 2 . In particular, in the structure of FIG. 2 , a distance between the free layer FL 1 and the second conductive line W 2 may be shorter than that of the structure of FIG. 1 . Accordingly, in the structure of FIG. 2 , the external magnetic field F EX generated by the second conductive line W 2 may be applied in a stronger intensity to the free layer FL 1 . Accordingly, an amount of a current that is required to generate the external magnetic field F EX for switching may be reduced. That is, the intensity of the second current I 2 applied to the second conductive line W 2 to generate the external magnetic field F EX may be lowered.

The structures of FIGS. 1 and 2 may further include an element for focusing the external magnetic field F EX on the free layer FL 1 (that is, a magnetic field focusing element). The magnetic field focusing element may include a cladding layer CR 1 provided on side walls of the second conductive line W 2 . FIGS. 3 and 4 are perspective views of the structures of FIGS. 1 and 2 including the cladding layer.

Referring to FIGS. 3 and 4 , the cladding layer CR 1 may be provided on side walls of the second conductive line W 2 . The cladding layer CR 1 may be formed of a magnetic material including at least one of Ni, Co, and Fe. For example, the cladding layer CR 1 may be a NiFe layer, a Co layer, a Fe layer, or the like. The cladding layer CR 1 may guide a magnetic flux generated from the second conductive line W 2 . Accordingly, an external magnetic field (F EX of FIGS. 1 and 2 ) occurring in the second conductive line W 2 may also be focused on the free layer F 1 by the cladding layer CR 1 . In addition, the cladding layer CR 1 may lead to an increase in the intensity of the external magnetic field (F EX of FIGS. 1 and 2 ). Accordingly, when the cladding layer CR 1 is included, the magnetization direction of the free layer F 1 may be easily switched.

The magnetic memory devices of FIGS. 1 through 4 may further include a switching device (not shown) connected to the magnetoresistive elements MR 1 and MR 1 ′. In this case, the second conductive line W 2 may be a part of the switching device. That is, a part of the switching device may be used as the second conductive line W 2 . When the magnetic memory devices of FIGS. 1 through 4 further include a switching device, the resultant structures are illustrated in FIGS. 5 through 8 .

FIGS. 5 through 8 illustrate detailed structures of magnetic memory devices according to example embodiments.

Referring to FIG. 5 , at least one transistor, for example, a first transistor TR 1 and a second transistor TR 2 may be provided on a substrate (not shown). The first transistor TR 1 may include a first source S 1 , a first drain D 1 , and a first gate line GL 1 . Although not illustrated, a first channel region may be disposed between the first source S 1 and the first drain D 1 . A first gate line GL 1 may be disposed on the first channel region. A first gate insulating layer GI 1 may be disposed between the first channel region and the first gate line GL 1 . The second transistor TR 2 may have a structure that is identical or similar to that of the first transistor TR 1 . That is, the second transistor TR 2 may include a second source S 2 , a second drain D 2 , and a second gate line GL 2 . A second channel region (not shown) may be disposed between the second source S 2 and the second drain D 2 . A second gate line GL 2 may be disposed on the second channel region. A second gate insulating layer GI 2 may be disposed between the second channel region and the second gate line GL 2 . In the present example embodiments, the first source S 1 and the second source S 2 may refer to a same region. That is, the first and second transistors TR 1 and TR 2 may share (or, alternatively, both may be connected to) one source S 1 /S 2 . Accordingly, the source S 1 /S 2 may be referred to as a ‘common source’. The first drain D 1 and the second drain D 2 may be spaced apart from each other with the common source S 1 /S 2 interposed therebetween. In addition, the first gate line GL 1 may be referred to as a first word line, and the second gate line GL 2 may be referred to as a second word line. The first and second gate lines GL 1 and GL 2 may extend in a Y-axis direction.

A first magnetoresistive element MR 1 may be disposed on (above) the first transistor TR 1 . The first magnetoresistive element MR 1 may be disposed on (above) the first gate line GL 1 . The first transistor TR 1 may be connected to the first magnetoresistive element MR 1 . The first drain D 1 of the first transistor TR 1 may be connected to a lower surface of the first magnetoresistive element MR 1 . The first drain D 1 and the lower surface of the first magnetoresistive element MR 1 may be connected to each other through a first connection plug CP 1 and a first connection layer CL 1 . A second magnetoresistive element MR 2 may be disposed on (above) the second transistor TR 2 . The second magnetoresistive element MR 2 may be disposed on (above) the second gate line GL 2 . The second transistor TR 2 may be connected to the second magnetoresistive element MR 2 . The second drain D 2 of the second transistor TR 2 may be connected to a lower surface of the second magnetoresistive element MR 2 . The second drain D 2 and the lower surface of the second magnetoresistive element MR 2 may be connected to each other through a second connection plug CP 2 and a second connection layer CL 2 . The connection structure of the first magnetoresistive element MR 1 and the first transistor TR 1 and the connection structure of the second magnetoresistive element MR 2 and the second transistor TR 2 may be symmetric about the common source S 1 /S 2 .

The first and second magnetoresistive elements MR 1 and MR 2 may have the same structure as that of the magnetoresistive element MR 1 of FIG. 1 . The first magnetoresistive element MR 1 may include the first separation layer SL 1 and the first free layer FL 1 which are sequentially stacked on the first pinned layer PL 1 , and the second magnetoresistive element MR 2 may include the second separation layer SL 2 and the second free layer FL 2 which are sequentially stacked on the second pinned layer PL 2 . That is, the first and second magnetoresistive elements MR 1 and MR 2 each may have a bottom-pinned structure.

A bit line BL 1 may be disposed on the first and second magnetoresistive elements MR 1 and MR 2 . The bit line BL 1 may be commonly connected to the first and second magnetoresistive elements MR 1 and MR 2 . The bit line BL 1 may commonly contact the first and second free layers FL 1 and FL 2 . The bit line BL 1 may extend in an X-axis direction. Accordingly, the bit line BL 1 may extend to cross the first and second gate lines GL 1 and GL 2 . At a point of intersection of the bit line BL 1 and the first and second gate lines GL 1 and GL 2 , the first and second magnetoresistive elements MR 1 and MR 2 may be located.

The bit line BL 1 of FIG. 5 may correspond to the first conductive line W 1 of FIG. 1 , and the first and second gate lines GL 1 and GL 2 of FIG. 5 may correspond to the second conductive line W 2 of FIG. 1 . Accordingly, in the structure of FIG. 5 , a magnetization direction of a first free layer FL 1 may be switched by a Rashba field generated in the first free layer FL 1 by the bit line BL 1 and an external magnetic field that is applied to the first free layer FL 1 by the first gate line GL 1 . Likewise, a magnetization direction of a second free layer FL 2 may be switched by a Rashba field generated in the second free layer FL 2 by the bit line BL 1 and an external magnetic field that is applied to the second free layer FL 2 by the second gate line GL 2 . A data writing method using the Rashba field and the external magnetic field will be described in detail below with reference to FIGS. 9A to 9D .

FIG. 6 is a perspective view of a magnetic memory device according to further example embodiments. The magnetic memory device according to present example embodiments is modified from the structure of FIG. 5 .

Referring to FIG. 6 , like the magnetic memory device of FIG. 5 , the magnetic memory device according to the present example embodiments may include the first and second transistors TR 1 and TR 2 . First and second magnetoresistive elements MR 1 ′ and MR 2 ′ may be respectively disposed on (above) the first and second transistors TR 1 and TR 2 . The first and second magnetoresistive elements MR 1 ′ and MR 2 ′ may each have a top-pinned structure. That is, the first magnetoresistive element MR 1 ′ may include the first separation layer SL 1 and the first pinned layer PL 1 which are sequentially stacked on the first free layer FL 1 , and the second magnetoresistive element MR 2 ′ may include the second separation layer SL 2 and the second pinned layer PL 2 which are sequentially stacked on the second free layer FL 2 . In this case, the first and second drains D 1 and D 2 may be connected to upper surfaces of the first and second magnetoresistive elements MR 1 ′ and MR 2 ′, respectively. The first drain D 1 may be connected to the upper surface of the first pinned layer PL 1 through a first connection plug CP 1 ′ and a first connection layer CL 1 ′. The second drain D 2 may be connected to the upper surface of the second pinned layer PL 2 through a second connection plug CP 2 ′ and a second connection layer CL 2 ′. The first connection layer CL 1 ′ and the second connection layer CL 2 ′ may each have a bent structure. In addition, the bit line BL 1 may be disposed under the first and second magnetoresistive element MR 1 ′, MR 2 ′. The bit line BL 1 may contact lower surfaces of the first and second free layers FL 1 and FL 2 . The first and second gate lines GL 1 and GL 2 may be spaced apart from the bit line BL 1 under the bit line BL 1 . Accordingly, the bit line BL 1 may be disposed between the gate lines GL 1 and GL 2 and the magnetoresistive elements MR 1 ′ and MR 2 ′. The first and second magnetoresistive elements MR 1 ′ and MR 2 ′ may be located at a point of intersection where the bit line BL 1 crosses the first and second gate lines GL 1 and GL 2 .

In the magnetic memory device of FIG. 6 , the first and second magnetoresistive elements MR 1 ′ and MR 2 ′ may correspond to the magnetoresistive element MR 1 ′ of FIG. 2 . In addition, the bit line BL 1 and gate lines GL 1 and GL 2 of FIG. 6 may respectively correspond to the first conductive line W 1 and the second conductive line W 2 of FIG. 2 . Even in the structure of FIG. 6 , magnetization directions of the free layers FL 1 and FL 2 may be switched by a Rashba field that is generated in the free layers FL 1 and FL 2 by the bit line BL 1 and an external magnetic field that is applied to the free layers FL 1 and FL 2 by the gate lines GL 1 and GL 2 .

In the structure of FIG. 6 , distances between the free layers FL 1 and FL 2 and the corresponding gate lines GL 1 and GL 2 may be shorter than that of FIG. 5 . Accordingly, in the structure of FIG. 6 , external magnetic fields generated by the first and second gate lines GL 1 and GL 2 may be applied having high amplitudes to the corresponding free layers FL 1 and FL 2 . Accordingly, the magnitude of a current that is required to generate an external magnetic field for switching may decrease. That is, the magnitude of a current applied to the first and second gate lines GL 1 and GL 2 to generate the external magnetic field may decrease.

The structures of FIGS. 5 and 6 may further include an element for focusing the external magnetic field generated by the first and second gate lines GL 1 and GL 2 on the corresponding free layers FL 1 and FL 2 (that is, a magnetic field focusing element). The magnetic field focusing element may include a cladding layer CR 1 /CR 2 provided on side walls of the first and second gate lines GL 1 and GL 2 .

FIGS. 7 and 8 are perspective views of the structures of FIGS. 5 and 6 including the cladding layer.

Referring to FIGS. 7 and 8 , a first cladding layer CR 1 may be disposed on side walls of the first gate line GL 1 , and a second cladding layer CL 2 may be disposed on side walls of the second gate line GL 2 . The first and second cladding layers CL 1 and CL 2 may be formed of a magnetic material including at least one of Ni, Co, and Fe. For example, the first and second cladding layers CL 1 and CL 2 may each be a NiFe layer, a Co layer, a Fe layer, or the like. The external magnetic field generated by the first gate line GL 1 may be focused on the first free layer FL 1 by the first cladding layer CR 1 . The external magnetic field generated by the second gate line GL 2 may be focused on the second free layer FL 2 by the second cladding layer CR 2 . In addition, the first and second cladding layers CR 1 and CR 2 may lead to an increase in the amplitude of the external magnetic field. Accordingly, when the first cladding layers CR 1 and CR 2 are provided, magnetization directions of the free layers FL 1 and FL 2 may be easily switched. When the cladding layers CR 1 and CR 2 are included as illustrated in FIGS. 7 and 8 , a first gate insulating layer GI 1 ′ may be disposed under the first gate line GL 1 and the first cladding layers CR 1 on both sides of first gate line GL 1 , and a second gate insulating layer GI 2 ′ may be disposed under the second gate line GL 2 and the second cladding layer CR 2 on both sides of the second gate line GL 2 . The magnetic memory devices of FIGS. 7 and 8 are the same as the magnetic memory devices of FIGS. 5 and 6 , except that the cladding layers CR 1 and CR 2 are additionally formed and the gate insulating layers GI 1 ′ and GI 2 ′ are somewhat modified.

Regarding the magnetic memory devices of FIGS. 5 through 8 , the gate lines GL 1 and GL 2 of the transistors TR 1 and TR 2 are used as conductive lines for generating an external magnetic field required for data writing (that is, switching of magnetization direction). Accordingly, the structure of the magnetic memory devices may be simplified. In a typical MRAM, because a separate digit line is disposed under an MTJ element, the structure of a manufactured memory device is complicated and the manufacturing process therefor may also be complicated. However, in the present example embodiments, the gate lines GL 1 and GL 2 are used as a conductive line for generating an external magnetic field. Accordingly, a separate digit line is not needed, and due to the absence of the digit line, simplification in terms of structure and process may be achieved. To use the gate lines GL 1 and GL 2 as the conductive line for generating the external magnetic field, the gate lines GL 1 and GL 2 may be formed of an excellent conductive material, such as metal.

When an external magnetic field is generated by using the first and second gate lines GL 1 and GL 2 to perform data writing, a selected voltage may be applied to a substrate (not shown) so as not to turn on the first and second transistors TR 1 and TR 2 . That is, without turning-on the first and second transistors TR 1 and TR 2 , a current may be provided to the first and second gate lines GL 1 and GL 2 to generate an external magnetic field. In other words, when an external magnetic field is generated by the first and second gate lines GL 1 and GL 2 , the first and second gate lines GL 1 and GL 2 may not operate having a gating function. Meanwhile, during data read, the first and second gate lines GL 1 and GL 2 may be used for ON/OFF of the first and second transistors TR 1 and TR 2 . For example, referring to FIG. 5 , when a selected voltage is applied to the first gate line GL 1 to turn on the first transistor TR 1 and then, a read current is provided between the first transistor TR 1 and the bit line BL 1 , data written on the first magnetoresistive element MR 1 may be read. In this regard, although the read current flows through the first magnetoresistive element MR 1 , due to the low intensity of the read current, a magnetization direction of the free layer FL 1 may not be changed by the read current. As described above, the first and second transistors TR 1 and TR 2 may be selectively driven during the data read.

Hereinafter, a method of operating a magnetic memory device, according to example embodiments, is described in detail.

FIGS. 9A through 9D are perspective views for explaining a data writing method of a magnetic memory device, according to example embodiments. The method according to the present example embodiments relates to the magnetic memory device of FIG. 5 .

Referring to FIG. 9A , a magnetic memory device having the structure of FIG. 5 is provided. In this regard, the first and second free layers FL 1 and FL 2 may be magnetized in a Z-axis direction. A first current I 11 may be applied to the bit line BL 1 to cause a Rashba field F RB1 in the first free layer FL 1 . When the first current I 11 is provided to the bit line BL 1 in a reverse X-axis direction, the Rashba field F RB1 may be applied in a Y-axis direction. Another Rashba field (not shown) which is the same as the Rashba field F RB1 may occur even in the second free layer FL 2 . A second current I 21 may be provided to the first gate line GL 1 to generate an external magnetic field F EX1 from the first gate line GL 1 . The external magnetic field F EX1 may be applied to the first free layer FL 1 . When the second current I 21 is provided in a Y-axis direction, the external magnetic field F EX1 may be applied to the first free layer FL 1 in a reverse X-axis direction or in a direction similar thereto. Accordingly, in the first free layer FL 1 , the application direction of the external magnetic field F EX1 may be perpendicular to that of the Rashba field F RB1 , or may be similar to the perpendicular direction. In the first free layer FL 1 , the application direction of the external magnetic field F EX1 may be identical or similar to the direction of the first current I 11 provided to the bit line BL 1 to induce the Rashba field F RB1 .

Due to the Rashba field F RB1 and the external magnetic field F EX1 , the magnetization direction of the first free layer FL 1 may be changed from the Z-axis direction to a reverse Z-axis direction. Due to the Rashba field F RB1 and the external magnetic field F EX1 which are perpendicular to each other, the magnetization (that is, a magnetic moment) of the first free layer FL 1 may be perturbed, and an axis of the magnetization (that is, a magnetic moment) may rotate on a particular orbital. The rotating of the axis of the magnetization (that is, magnetic moment) on a particular orbital is referred to as a precession. As such, while the precession of the magnetization of the first free layer FL 1 , the magnetization direction may be switched to the reverse Z-axis direction. That is, when the Rashba field F RB1 is applied in the Y-axis direction and the external magnetic field F EX1 is applied in the reverse X-axis direction, the Rashba field F RB1 and the external magnetic field F EX1 may affect the magnetization of the first free layer FL 1 such that the magnetization direction is changed to the reverse Z-axis direction. Thus, the magnetization direction of the first free layer FL 1 may be switched from the Z-axis direction to the reverse Z-axis direction. The switching result of the magnetization direction of the first free layer FL 1 illustrated in FIG. 9A to the reverse Z-axis direction is illustrated in FIG. 9B . The first magnetoresistive element MR 1 illustrated in FIG. 9B may be considered as having a first data written thereon.

Referring to FIG. 9C , in a state where the first free layer FL 1 is magnetized in the reverse Z-axis, a first current I 12 may be provided to the bit line BL 1 and a second current I 22 may be provided to the first gate line GL 1 . Due to the first current I 12 provided to the bit line BL 1 , a Rashba field F RB2 may occur in the first free layer FL 1 . When the first current I 12 is provided in the X-axis direction, the Rashba field F RB2 may occur in the reverse Y-axis direction. Here, the same Rashba field (not shown) may occur in the second free layer FL 2 . Due to the second current I 22 provided to the first gate line GL 1 , an external magnetic field F EX2 may be applied to the first free layer FL 1 . The second current I 22 may be provided in the reverse Y-axis direction, and the external magnetic field F EX2 may be applied to the first free layer FL 1 in the X-axis direction (or a direction similar thereto). Accordingly, the application direction of the external magnetic field F EX2 in the first free layer FL 1 may be perpendicular to the direction of the Rashba field F RB2 , or may be similar to the perpendicular direction. In the first free layer FL 1 , the application direction of the external magnetic field F EX2 may be identical or similar to the direction of the first current I 12 provided to the bit line BL 1 to induce the Rashba field F RB2 .

Due to the Rashba field F RB2 and the external magnetic field F EX2 , the magnetization direction of the first free layer FL 1 may be switched from in the reverse Z-axis direction to the Z-axis direction. Due to the Rashba field F RB2 and the external magnetic field F EX2 , the magnetization (that is, a magnetic moment) of the first free layer FL 1 may be precessed, and switched to the Z-axis direction. That is, when the Rashba field F RB2 is applied in the reverse Y-axis direction and the external magnetic field F EX2 is applied in the X-axis direction, due to the Rashba field F RB2 and the external magnetic field F EX2 , the magnetization of the first free layer FL 1 may be forced toward the Z-axis direction. Thus, the magnetization direction of the first free layer FL 1 may be switched from the reverse Z-axis direction to the Z-axis direction. The switching result of the magnetization direction of the first free layer FL 1 illustrated in FIG. 9C to the Z-axis direction is illustrated in FIG. 9D . The first magnetoresistive element MR 1 illustrated in FIG. 9D may be considered as having a second data written thereon.

In a method similar to the method described with reference to FIGS. 9A to 9D , the magnetization direction of the second free layer FL 2 may be switched. That is, a first current may be provided to the bit line BL 1 and a second current may be provided to the second gate line GL 2 to apply a Rashba field and an external magnetic field perpendicular to the Rashba field to the second free layer FL 2 , thereby switching the magnetization direction of the second free layer FL 2 .

During data writing as described above, the first and second transistors TR 1 and TR 2 may not operate, that is, may be turned off. Without turning on the first and second transistors TR 1 and TR 2 , at least one of the first and second gate lines GL 1 and GL 2 may be used to generate a magnetic field (that is, the external magnetic field). When the first and second gate lines GL 1 and GL 2 are used as a conductive line for generating a magnetic field (that is, the external magnetic field) to perform data writing, a selected voltage may be applied to a substrate (not shown) so as not to turn on the first and second transistors TR 1 and TR 2 .

In the present example embodiments, the magnetization directions of the free layers FL 1 and FL 2 may be perpendicularly switched by using the Rashba fields F RB1 and F RB2 and the external magnetic fields F EX1 and F EX2 to write data on the first and second magnetoresistive elements MR 1 and MR 2 . In this regard, the Rashba fields F RB1 and F RB2 may occur due to the first currents I 11 and I 12 flowing through the bit line BL 1 , and the external magnetic fields F EX1 and F EX2 may occur due to the second currents I 21 and I 22 flowing through the gate lines GL 1 and GL 2 . Accordingly, a current (that is, I 11 /I 21 or I 12 /I 22 ) for writing may not flow through the first and second magnetoresistive elements MR 1 and MR 2 .

In a typical STT-MRAM, a magnetization direction of a free layer is switched by using a current flowing through a magnetoresistive element (that is, an MTJ element). Accordingly, a separation layer (that is, a tunneling layer) of the magnetoresistive element (that is, an MTJ element) needs to have very high endurance. Also, because ranges of a writing voltage (that is, a switching voltage) and a read voltage need to be determined within a voltage range in which the separation layer (that is, a tunneling layer) is not broken down, there are many limitations to set a range of an operation voltage (writing voltage and read voltage). When a distribution (range) of the writing voltage and a distribution (range) of the read voltage are close to a distribution (range) of a breakdown voltage of the separation layer (that is, tunneling layer), an operation error, such as a writing error, and reliability related problems may occur. To suppress these problems, the distribution (range) of the writing voltage, the distribution (range) of the read voltage, and the distribution (range) of the breakdown voltage need to be strictly managed (controlled). These problems may make commercialization of STT-MRAM difficult.

However, in the present example embodiments, a current does not flow through the first and second magnetoresistive elements MR 1 and MR 2 , and a current is provided to only the bit line BL 1 and the first and second gate lines GL 1 and GL 2 to switch the magnetization directions of the free layers FL 1 and FL 2 . That is, in the present example embodiments, currents for switching the magnetization direction of the free layers FL 1 and FL 2 , that is, the first currents I 11 and I 12 and the second currents I 21 and I 22 , do not flow through the first and second magnetoresistive elements MR 1 and MR 2 . Accordingly, in the present example embodiments, any damage to the separation layers SL 1 and SL 2 (that is, a tunneling layer) of the first and second magnetoresistive elements MR 1 and MR 2 by a switching current (that is, a writing current) or deterioration of characteristics of the separation layers SL 1 and SL 2 may be prevented. Accordingly, endurance requirement conditions with respect to the separation layers SL 1 and SL 2 (that is, a tunneling layer) may be relieved, and deterioration of characteristics of the first and second magnetoresistive elements MR 1 and MR 2 by the writing current may be prevented. In addition, although the read current may be applied to flow through the first and second magnetoresistive elements MR 1 and MR 2 , the intensity of the read current is much lower than that of the writing current of a typical STT-MRAM, the damage to the separation layers SL 1 and SL 2 (that is, a tunneling layer) by the read current or deterioration of the separation layers SL 1 and SL 2 by the read current may not occur. Also, in the present example embodiments, because the writing current does not flow through the first and second magnetoresistive elements MR 1 and MR 2 , there is no need to consider a distribution (range) of a writing voltage with respect to the first and second magnetoresistive elements MR 1 and MR 2 . That is, regarding the first and second magnetoresistive elements MR 1 and MR 2 , only the distribution (range) of a read voltage and the distribution (range) of a breakdown voltage may be taken into consideration. Accordingly, requirements for the management of an operation voltage are relieved, and a range of the operation voltage may be freely set, and the possibility of occurrence of an operation error may be lowered. Thus, a device structure according to example embodiments may be advantageous for commercialization of an MRAM.

Also, a typical STT-MRAM requires a large-size cell transistor to switch the magnetization direction of a free layer. That is, when a material with high magnetic anisotropy energy is used as a free layer material to obtain data retention characteristics of a free layer, the magnitude of a current (that is, a switching current) that is required to switch the magnetization direction of the free layer increases, leading to a need for a large-size cell transistor. However, in the present example embodiments, there is no need for manufacturing a cell transistor, that is, the first and second transistors TR 1 and TR 2 , in large size. This is because during data writing, a writing current is not applied from the first and second transistors TR 1 and TR 2 . To perform data writing, the first current I 11 or I 12 is provided to the bit line BL 1 and the second current I 21 or I 22 is provided to the gate lines GL 1 and GL 2 , and these currents may be driven by a driving device of a peripheral circuit unit. Manufacturing a large driving device of a peripheral circuit unit is easier than manufacturing a large cell transistor, and the size of the driving device may not affect the overall size of a device. Accordingly, a magnetic memory device according to example embodiments may be suitable for high integration and high densification.

Additionally, in the case of a typical MRAM in which a magnetization direction of a free layer is switched using a digit line and a bit line, the use of an MTJ element having a horizontal magnetization and a relatively complicated structure make it difficult to realize high-densification. In addition, in the typical MRAM, even a cell adjacent to a target cell that is to be switched may be switched or half-switched. This phenomenon is referred to as a cross talk. However, in the case of a magnetic memory device according to example embodiments, magnetoresistive elements MR 1 and MR 2 having a perpendicular magnetization are used and also, the magnetic memory device has a more simplified structure than the typical MRAM. Thus, the magnetic memory device according to example embodiments is suitable for high integration and high densification. Also, in a magnetic memory device according to example embodiments, the Rashba fields F RB , and F RB2 affect only inside the free layer FL 1 , and do not affect outside of the free layer FL 1 . Accordingly, the cross talk may be prevented or suppressed.

FIG. 10 is a perspective view for explaining a data read method of a magnetic memory device according to example embodiments.

Referring to FIG. 10 , after the first transistor TR 1 is turned on, a read current RC 1 may be applied between the first transistor TR 1 and the bit line BL 1 . The read current RC 1 may flow through the first magnetoresistive element MR 1 . Data written on the first magnetoresistive element MR 1 may be identified by measuring a resistance of the first magnetoresistive element MR 1 by providing the read current RC 1 to the first magnetoresistive element MR 1 . When the magnetization direction of the first pinned layer PL 1 and the magnetization direction of the first free layer FL 1 are parallel (in a same direction), the first magnetoresistive element MR 1 may have a low resistance, and when the magnetization direction of the first pinned layer PL 1 and the magnetization direction of the first free layer FL 1 are anti-parallel (in an opposite direction), the first magnetoresistive element MR 1 may have a high resistance.

During data reading as described above, the first and second gate lines GL 1 and GL 2 may be used for turning ON/OFF of the first and second transistors TR 1 and TR 2 . That is, a selected voltage is applied to the first gate line GL 1 to turn on the first transistor TR 1 , and then, the read current RC 1 may be provided between the first transistor TR 1 and the bit line BL 1 . Although the read current RC 1 flows through the first magnetoresistive element MR 1 , because the intensity of the read current RC 1 is low, the magnetization direction of the first free layer FL 1 may not be changed. The first and second transistors TR 1 and TR 2 may be selectively driven only when data reading is performed. Because the magnitude of the current (the read current) provided by the first and second transistors TR 1 and TR 2 is low, sizes of the first and second transistors TR 1 and TR 2 may be small.

The operation methods explained with reference to FIGS. 9A through 9D and 10 relate to the structure of FIG. 5 . However, these operation methods may also be applied to the structures of FIGS. 6 through 8 in a similar manner. This may be obvious to one of ordinary skill in the art, and thus, a detailed description thereof is not presented herein.

In the description above, the magnetic memory devices and the operation methods according to the above example embodiments have been described in detail. However, the description does not limit the scope, and is presented to provide only examples of detailed embodiments. For example, one of ordinary skill in the art may know that the magnetic memory devices of FIGS. 1 through 8 may be variously changed. In detail, each of the magnetoresistive elements MR 1 , MR 1 ′, MR 2 , and MR 2 ′ may further include at least one layer other than the pinned layers PL 1 and PL 2 , the separation layers SL 1 and SL 2 , and the free layers FL 1 and FL 2 . Also, in the structures of FIGS. 5 through 8 , the bit line BL 1 may be repeatedly arranged in the Y-axis direction, and the gate lines GL 1 and GL 2 may be repeatedly arranged in the X-axis direction, and at intersection points thereof, the magnetoresistive elements MR 1 and MR 2 may be provided. In addition, one of ordinary skill in the art may know that the operation methods explained with reference to FIGS. 9A through 9D and FIG. 10 may be variously changed. Also, a structure according to example embodiments may be applied to, in addition to a memory device, other devices, for example, a non-volatile logic device. Accordingly, the scope is defined not by the above example embodiments but by the technical features recited in the claims.