HAMR media structure with intermediate layer underlying a magnetic recording layer having multiple sublayers

Energy/Heat Assisted Magnetic Recording (EAMR/HAMR) systems can potentially increase the areal density of information recorded magnetically on various media. For example, to achieve magnetic information storage levels beyond 1 terabit per inch squared, smaller grain size media may be required. Such designs can demand higher Ku materials for a magnetic recording layer to sustain thermal stability, such as L1 0 ordered FePt alloys.

The layer beneath the FePt magnetic recording layer (e.g., intermediate layer or underlayer) may be important to the media design to achieve the desired microstructure of the FePt magnetic recording layer. For example, one aspect controlling the FePt microstructure is the interfacial energy between the FePt magnetic recording layer and the intermediate layer, which varies depending on the segregant in the FePt magnetic recording layer and the intermediate layer properties. Recently, HAMR media including FePt magnetic recording layers has been optimized in terms of microstructure and magnetic properties using an MgO intermediate layer, together with a carbon segregant in the FePt magnetic recording layer.

However, when using intermediate layers other than MgO, carbon may not be an ideal segregant. For example, other intermediate layer materials may cause carbon to diffuse away from the intermediate layer interface, resulting in the formation of larger interconnected FePt grains. Accordingly, an improved HAMR media structure that addresses these shortcomings is needed.

FIG. 1 is a top schematic view of a disk drive configured for heat assisted magnetic recording (HAMR) and including a magnetic medium with a FePt magnetic recording layer, intermediate layer and underlayer in accordance with one embodiment of the invention.

FIG. 2 is a side cross sectional schematic view of selected components of the HAMR system of FIG. 1 including the magnetic medium with the FePt magnetic recording layer, intermediate layer and underlayer in accordance with one embodiment of the invention.

FIG. 3 is side cross sectional view of a HAMR medium having a FePt magnetic recording layer, intermediate layer and underlayer in accordance with one embodiment of the invention.

FIG. 4 illustrates exemplary X-ray diffraction (XRD) patterns exemplifying perpendicular textures of FePt magnetic recording layers on TiON intermediate layers at different sputter oxygen percentages of the TiON intermediate layer in accordance with one embodiment of the invention.

FIG. 5A illustrates exemplary magnetic properties of HAMR media with an FePt—AgC magnetic recording layer on a TiON intermediate layer at different sputter oxygen percentages of the TiON intermediate layer in comparison with the magnetic property of an FePt—AgC magnetic recording layer on an MgO intermediate layer in accordance with one embodiment of the invention.

FIG. 5B illustrates exemplary magnetic properties of HAMR media with an FePt—AgBN magnetic recording layer on a TiON intermediate layer at different sputter oxygen percentages of the TiON intermediate layer in comparison with the magnetic property of an FePt—AgC magnetic recording layer on an MgO intermediate layer in accordance with one embodiment of the invention.

FIGS. 6A and 6B are plan transmission electron microscope (TEM) views of HAMR media with an FePt—AgBN magnetic recording layer on a TiON intermediate layer and an FePt—AgC magnetic recording layer on an MgO intermediate layer in accordance with one embodiment of the invention.

FIG. 7 is a flowchart of a process for manufacturing a HAMR medium including a FePt magnetic recording layer, an intermediate layer and an underlayer in accordance with one embodiment of the invention.

Referring now to the drawings, embodiments of heat assisted magnetic recording (HAMR) media that include a heat sink layer, an underlayer on the heat sink layer, an intermediate layer on the underlayer, and an FePt magnetic recording layer on the intermediate layer are illustrated. One such HAMR media design includes a FePt magnetic recording layer having a first FePt magnetic recording sublayer on the intermediate layer, a second FePt magnetic recording sublayer on the first FePt magnetic recording sublayer and a third FePt magnetic recording sublayer on the second FePt magnetic recording sublayer. Each of the FePt magnetic recording sublayers includes a different segregant. The segregant in the first FePt magnetic recording sublayer and the material used for the intermediate layer are selected to produce a substantially uniform distribution of segregant at the interface between the first FePt magnetic recording sublayer and the intermediate layer, thereby resulting in a substantially uniform FePt granular microstructure. In an aspect, an intermediate layer of TiON, VON, CrON, TiOC, VOC, TiONC, VONC, and/or combinations thereof, is utilized together with a segregant of AgBN, AgCN, AgBNC, AgB 2 O 3 , AgMoO 3 , AgV 2 O 5 , B 2 O 3 , MoO 3 , V 2 O 5 , and/or combinations thereof, in the first FePt magnetic recording sublayer.

The terms “above,” “over,” “on,” “below,” “under,” and “between” as used herein refer to a relative position of one layer with respect to other layers. As such, one layer deposited or disposed above, over, on, below, or under another layer may be directly in contact with the other layer or may have one or more intervening layers. Moreover, one layer deposited or disposed between layers may be directly in contact with the layers or may have one or more intervening layers.

It shall be appreciated by those skilled in the art in view of the present disclosure that although various exemplary fabrication methods are discussed herein with reference to magnetic recording disks, the methods, with or without some modifications, may be used for fabricating other types of recording disks, for example, optical recording disks such as a compact disc (CD) and a digital-versatile-disk (DVD), or magneto-optical recording disks, or ferroelectric data storage devices.

FIG. 1 is a top schematic view of a disk drive 100 configured for heat assisted magnetic recording (HAMR) and including a magnetic medium 102 with an FePt magnetic recording layer having multiple sublayers and intermediate layer underlying the FePt magnetic recording layer (not shown in FIG. 1 , but see FIG. 3 ) in accordance with one embodiment of the invention. The laser (not visible in FIG. 1 , but see FIG. 2 ) is positioned with a head/slider 108 . Disk drive 100 may include one or more disks/media 102 to store data. Disk/media 102 resides on a spindle assembly 104 that is mounted to drive housing 106 . Data may be stored along tracks in the magnetic recording layer of disk 102 . The reading and writing of data is accomplished with the head 108 that may have both read and write elements. The write element is used to alter the properties of the magnetic recording layer of disk 102 and thereby write information thereto. In one embodiment, head 104 may have magneto-resistive (MR), or giant magneto-resistive (GMR) elements. In another embodiment, head 104 may be another type of head, for example, an inductive read/write head or a Hall Effect head.

In operation, a spindle motor (not shown) rotates the spindle assembly 104 , and thereby rotates disk 102 to position head 108 at a particular location along a desired disk track. The position of head 104 relative to disk 102 may be controlled by position control circuitry 110 .

FIG. 2 is a side cross sectional schematic view of selected components of the HAMR system of FIG. 1 including the magnetic medium 102 with the FePt magnetic recording layer having multiple sublayers and intermediate layer underlying the FePt magnetic recording layer (not shown in FIG. 2 , but see FIG. 3 ) in accordance with one embodiment of the invention. The HAMR system components also include a sub-mount 112 attached to a top surface of the slider 108 . A laser 114 is attached to the sub-mount 112 , and possibly to the slider 108 . The slider 108 includes the write element and the read element positioned along an air bearing surface (ABS) of the slider for writing information to, and reading information from, respectively, the media 102 .

In operation, the laser 114 is configured to direct light energy to a waveguide in the slider 108 which directs the light to a near field transducer (NFT) near the air bearing surface (e.g., bottom surface) of the slider. Upon receiving the light from the laser via the waveguide, the NFT generates localized heat energy that heats a portion of the media 102 near the write element and the read element. FIGS. 1 and 2 illustrate a specific embodiment of a HAMR system. In other embodiments, the improved media with the FePt magnetic recording layer and intermediate layer can be used in other suitable HAMR systems.

FIG. 3 is side cross sectional view of a HAMR medium 200 having a magnetic recording layer 214 with multiple sublayers and an intermediate layer 212 underlying the magnetic recording layer 214 in accordance with one embodiment of the invention. The medium 200 has a stacked structure with a glass substrate 202 at a bottom/base layer, an adhesion layer 204 on the glass substrate 202 , a seed layer 206 on the adhesion layer 204 , a heat sink layer 208 on the seed layer 206 , an underlayer 210 on the heat sink layer 208 , the intermediate layer 212 on the underlayer 210 , the magnetic recording layer 214 on the intermediate layer 212 , and a carbon overcoat layer 222 on the magnetic recording layer 214 . In some embodiments, the adhesion layer 204 , seed layer 206 , and carbon overcoat layer 222 can be omitted from the medium structure.

The magnetic recording layer 214 includes a first magnetic recording sublayer 216 on the intermediate layer 212 , a second magnetic recording sublayer 218 on the first magnetic recording sublayer 216 , and a third magnetic recording sublayer 220 on the second magnetic recording sublayer 218 . Each of the magnetic recording sublayers 216 , 218 , and 220 is made of FePt. In an exemplary embodiment, each of the magnetic recording sublayers 216 , 218 , and 220 includes L1 0 phase FePt. Providing three sublayers in the FePt magnetic recording layer 214 enables growth of columnar and thick granular media, which results in low roughness, improved read-back signal and improved overall media performance.

Each of the magnetic recording sublayers 216 , 218 , and 220 includes one or more segregants. In one embodiment, the segregant included in each of the magnetic recording sublayers is different. The segregant in the first FePt magnetic recording sublayer 216 and the material used for the intermediate layer 212 are selected to produce a substantially uniform distribution of segregant at the interface between the first FePt magnetic recording sublayer 216 and the intermediate layer 212 , thereby resulting in a substantially uniform FePt granular microstructure. In one instance, a substantially uniform FePt granular microstructure is produced when the FePt grain diameter is between about 7.5 nm and about 8.5 nm with a standard deviation of between about 2.5 nm and about 3.5 nm. In one embodiment, an intermediate layer 212 of TiON, VON, CrON, TiOC, VOC, TiONC, VONC, and/or combinations thereof, is utilized together with a segregant of AgBN, AgCN, AgBNC, AgB 2 O 3 , AgMoO 3 , AgV 2 O 5 , B 2 O 3 , MoO 3 , V 2 O 5 , and/or combinations thereof, in the first FePt magnetic recording sublayer 216 . In other embodiments, the segregant in the first magnetic recording sublayer may include other oxide, nitride or carbide segregants that have a surface energy less than 0.1 Joules per meter squared (J/m 2 ).

For example, in an exemplary embodiment, the intermediate layer 212 includes TiO x N (1-x) , where x is between about 0.4 and about 0.5. In another exemplary embodiment, the segregant in the first magnetic recording sublayer 216 includes AgBN. In a further exemplary embodiment, the first magnetic recording sublayer 216 includes an AgBN segregant having a BN content in the AgBN segregant that may be between about 25 mole percent and about 40 mole percent. In still a further exemplary embodiment, the first magnetic recording sublayer 216 includes an AgBN segregant and the intermediate layer 212 includes TiON.

In one embodiment, the underlayer 210 can be made of one or more materials such as TiN, CrN, VN, TiC, VC, RuAl, RuTi, FeAl, SrTiO 3 , BaTiO 3 , BaSnO 3 , MgO, W, Mo, Cr, NiAl, combinations thereof, and/or other suitable materials known in the art. For example, in an exemplary embodiment, the underlayer 210 includes TiN and the intermediate layer includes TiON.

In several embodiments, the intermediate layer 212 operates as a thermal barrier layer. For example, the intermediate layer 212 may be configured to (e.g., the materials for the intermediate layer are selected to) facilitate a heat transfer from the magnetic recording layer 214 to the heat sink layer 208 , and impede a heat transfer from the heat sink layer 208 to the magnetic recording layer 214 .

In several embodiments, the thermal conductivity (κ) of the intermediate layer 212 is less than the thermal conductivity of the underlayer 210 . For example, in embodiments in which the intermediate layer 212 includes TiO x N (1-x) (where x=0.4 to 0.5) and the underlayer 210 includes TiN, the thermal conductivity of TiO x N (1-x) is about 5 Watts per meter Kelvin (W/mK), whereas the thermal conductivity of TiN is about 10 W/mK. This can also be compared to the thermal conductivity of MgO, which is around 10 W/mK. Thus, utilizing an intermediate layer 212 of TiO x N (1-x) underneath the magnetic recording layer provides improved thermal conductivity properties of the HAMR medium 200 as compared to using MgO as the intermediate layer.

In addition, TiO x N (−x) may further provide improved optical properties over that provided by MgO. For example, the plasmonic effect observable in TiON may improve the optical impedance of the HAMR medium 200 during writing operations. Furthermore, the use of TiON may also result in similar or better magnetic performance in the magnetic recording layer(s) than the use of MgO.

In one embodiment, the segregant in the second magnetic recording sublayer 218 can be made of one or more materials such as BNC, BN, combinations thereof, and/or other suitable materials known in the art. In addition, the segregant in the third magnetic recording sublayer 220 can be made of one or more materials such as BNSiO 2 , BNZrO 2 , BNTa 2 O 5 , combinations thereof, and/or other suitable materials known in the art.

In one embodiment, the substrate 202 can be made of one or more materials such as an Al alloy, NiP plated Al, glass, glass ceramic, and/or combinations thereof. In one embodiment, the adhesion layer 204 can includes one or more materials such as CrTa, NiTa, combinations thereof, and/or other suitable materials known in the art.

In one embodiment, the seed layer 206 can be made of one or more materials such as RuAl, Cr, combinations thereof, and/or other suitable materials known in the art. In one embodiment, the heat sink layer 208 can be made of one or more materials such as W, Mo, Cr, Ru, Cu, Ag, Cu alloy, Ag alloy, combinations thereof, and/or other suitable materials known in the art.

In one embodiment, an intermediate layer 212 of TiON is deposited using a non-reactive sputtering process with a composite target of TiON. In another embodiment, an underlayer 210 of TiN and an intermediate layer 212 of TiON are sputter-deposited using a pure TiN target with a two-step process in one chamber. In the first step, the TiN underlayer 210 can be sputter-deposited first using pure Ar gas. Then, in the second step, the TiON intermediate layer 212 can be formed using a dc-reactive sputtering process in a mixture of Ar and O 2 gas. In an aspect, the amount of oxygen in the TiON intermediate layer can be tuned by varying the ratio of the Ar/O 2 flow rate to maximize the texture quality of the FePt magnetic recording layer. For example, the O 2 content in the Ar/O 2 mixture can vary between about 1.6 percent and about 1.8 percent, thus producing an intermediate layer of TiO x N (1-x) , where x is between about 0.4 and about 0.5. In addition, as the oxygen percentage increases, the transmittance and reflectance of the TiON intermediate layer increases. Therefore, in embodiments in which higher transmittance and reflectance of the TiON intermediate layer are desired, the O 2 content percentage can be greater than or equal to 1.8 percent. However, at O 2 content percentages higher than 1.8 percent, the FePt texture quality may degrade.

FIG. 4 illustrates exemplary X-ray diffraction (XRD) patterns 300 exemplifying perpendicular textures of FePt magnetic recording layers on TiON intermediate layers at different sputter oxygen percentages of the TiON intermediate layer in accordance with one embodiment of the invention. Each XRD pattern 300 provides a measurement of the intensity over a range of angles (2θ) of the detector. A baseline XRD pattern 302 illustrates the intensity of a FePt—C magnetic recording layer over an MgO intermediate layer. Pronounced peaks of the FePt magnetic recording layer with (001) and (002) texture appear in the baseline XRD pattern 302 , indicating a high quality FePt magnetic recording layer (good FePt microstructure/texture).

Each XRD pattern behind the baseline XRD pattern illustrates the intensity of a FePt—AgBN magnetic recording layer over a TiON intermediate layer at a particular sputter oxygen percentage of TiON. The O 2 percentage utilized in the dc-reactive sputtering process of TiON increases from 0 percent in the first XRD pattern 304 behind the baseline XRD pattern 302 to 2.5 percent in the last XRD pattern 306 . As can be seen in FIG. 4 , XRD pattern 308 , representing an O 2 percentage between about 1.6 and 1.8, provides the best texture and is comparable to the texture achieved using MgO, as observed in the baseline XRD pattern 302 . In addition to the FePt magnetic recording layer (001) and (002) peaks, the intermediate layer (TiON/MgO) and underlayer (RuAl) peaks can also be observed from FIG. 4 .

FIG. 5A illustrates exemplary magnetic properties of HAMR media with an FePt—AgC magnetic recording layer on a TiON intermediate layer at different sputter oxygen percentages of the TiON intermediate layer (TiON UL) in comparison with the magnetic property of an FePt—AgC magnetic recording layer on an MgO intermediate layer (MgO—POR) in accordance with one embodiment of the invention. As can be seen in FIG. 5A , the coercivity (Hc) of an FePt—AgC magnetic recording layer on an MgO intermediate layer (MgO—POR) is about 40 kiloOersteds (kOe). By comparison, the coercivity of a FePt—AgC magnetic recording layer on a TiON intermediate layer (TiON UL) varies between about 10 kOe and 30 kOe, depending on the O 2 content percentage used during dc-reactive sputtering of the TiON intermediate layer. The maximum coercivity of about 30 kOe occurs at an O 2 sputter content of about 1.8 percent. Thus, the magnetic properties of a FePt magnetic recording layer including a carbon segregant are adversely affected when deposited over a TiON intermediate layer.

FIG. 5B illustrates exemplary magnetic properties of HAMR media with an FePt—AgBN magnetic recording layer on a TiON intermediate layer at different sputter oxygen percentages of the TiON intermediate layer (TiON UL) in comparison with the magnetic property of an FePt—AgC magnetic recording layer on an MgO intermediate layer (MgO—POR) in accordance with one embodiment of the invention. As can be seen in FIG. 5B , the coercivity of an FePt—AgBN magnetic recording layer on a TiON intermediate layer (TiON UL) varies between about 20 kOe and 40 kOe, depending on the O 2 content percentage used during dc-reactive sputtering of the TiON intermediate layer. The maximum coercivity of about 40 kOe occurs at an O 2 sputter content of about 1.6 percent. The maximum coercivity of the FePt—AgBN magnetic recording layer at about 1.6 percent O 2 content of the TiON intermediate layer (TiON UL) is approximately equal that of the FePt—AgC magnetic recording layer on MgO (MgO—POR). Therefore, similar magnetic properties to that found in FePt—C magnetic recording layers deposited over an MgO intermediate layer can be achieved by using a BN segregant in the FePt magnetic recording layer deposited over a TiON intermediate layer.

FIGS. 6A and 6B are plan transmission electron microscope (TEM) views of HAMR media with an FePt—AgBN magnetic recording layer on a TiON intermediate layer and an FePt—AgC magnetic recording layer on an MgO intermediate layer in accordance with one embodiment of the invention. As can be seen by comparing FIGS. 6A and 6B , the microstructure of the FePt—AgBN magnetic recording layer deposited over a TiON intermediate layer is similar to the microstructure of the FePt—AgC magnetic recording layer deposited on an MgO intermediate layer.

FIG. 7 is a flowchart of a process 400 for manufacturing a HAMR medium including a FePt magnetic recording layer, an intermediate layer and an underlayer in accordance with one embodiment of the invention. In particular embodiments, the process 400 can be used to manufacture the HAMR magnetic media of FIG. 3 , FIG. 2 , or FIG. 1 . The process first provides a substrate in block 402 . The process then provides a heat sink layer on the substrate in block 404 . The process then provides an underlayer on the heat sink layer in block 406 . The process then provides an intermediate layer on the underlayer in block 408 . The process then provides a magnetic recording layer including three magnetic recording sublayers on the intermediate layer in block 410 .

In a number of embodiments, the process can manufacture the layers of the HAMR medium with any of the numerous variations described above for the embodiments of FIGS. 1, 2 , and 3 . For example, in one such case, the process can also provide an adhesion layer between the substrate and the heat sink layer, a seed layer between the adhesion layer and the heat sink layer, and a carbon overcoat layer on the magnetic recording layer.

In several embodiments, the layers can include the materials described above. For example, the process may provide the underlayer on the heat sink layer by depositing a layer of TiN, CrN, RuAl, SrTiO 3 , MgO, W, Mo, Cr, NiAl, and/or combinations thereof on the heat sink layer. In addition, the process may provide the intermediate layer on the underlayer by depositing a layer of TiON, VON, CrON, TiOC, VOC, TiONC, and/or combinations thereof on the underlayer.

In some embodiments, the process provides the underlayer on the heat sink layer by sputter-depositing the underlayer using a pure TiN target in pure Ar gas to produce a TiN underlayer. In some embodiments, the process provides the intermediate layer on the underlayer by dc-reactive sputtering the intermediate layer using a pure TiN target in mixed Ar/O 2 gas to produce a TiON intermediate layer. For example, the O 2 content percentage in the mixed Ar/O 2 gas may be between about 1.6 and 1.8. In some embodiments, the process provides the intermediate layer on the underlayer by using a non-reactive sputtering process with a composite target of TiON.

In some embodiments, the process provides the magnetic recording layer by sputter-depositing the FePt—X granular magnetic recording sublayers onto the TiON/TiN layers. For example, the segregant used in the first magnetic recording sublayer may include AgBN, AgCN, AgBNC, AgB 2 O 3 , AgMoO 3 , AgV 2 O 5 , B 2 O 3 , MoO 3 , V 2 O 5 , and/or combinations thereof. As another example, the segregant used in the second magnetic recording sublayer may include BNC, BN, and/or combinations thereof. As yet another example, the segregant used in the third magnetic recording sublayer may include BNSiO 2 , BNZrO 2 , BNTa 2 O 5 , and/or combinations thereof.

In one embodiment, the process can perform the sequence of actions in a different order. In another embodiment, the process can skip one or more of the actions. In other embodiments, one or more of the actions are performed simultaneously. In some embodiments, additional actions can be performed.

While the above description contains many specific embodiments of the invention, these should not be construed as limitations on the scope of the invention, but rather as examples of specific embodiments thereof. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their equivalents.