SOT READER WITH RECESSED SOT TOPOLOGICAL INSULATOR MATERIAL

The present disclosure generally relates to spin-orbit torque (SOT) devices comprising a bismuth antimony (BiSb) layer. The SOT devices further comprises a first shield, a BiSb layer disposed over the first shield (S1), a free layer (FL) disposed over the BiSb layer, and a second shield (S2) disposed over the FL. The S1, the FL, and the S2 are disposed at a media facing surface (MFS). The BiSb layer is recessed from the MFS a first distance of about 5 nm to about 20 nm. The FL has a length greater than the first distance. A notch and/or an insulation layer is disposed adjacent to the BiSb layer at the MFS. Current may be configured to flow vertically through the S2 to the FL, and horizontally from the FL to the BiSb layer. Current may be configured to flow vertically through the S2 to the S1.

BACKGROUND OF THE DISCLOSURE

Field of the Disclosure

Embodiments of the present disclosure generally relate to spin-orbit torque (SOT) device comprising a bismuth antimony (BiSb) layer.

Description of the Related Art

BiSb layers are narrow band gap topological insulators with both giant spin Hall effect and high electrical conductivity. BiSb is a material that has been proposed in various spin-orbit torque (SOT) device applications, such as for a spin Hall layer for magnetoresistive random access memory (MRAM) devices and energy-assisted magnetic recording (EAMR) write heads.

However, utilizing BiSb materials in commercial SOT applications can present several obstacles. For example, BiSb materials have low melting points, large grain sizes, significant Sb migration issues upon thermal annealing due to its film roughness, difficulty maintaining a desired (012) or (001) orientation for maximum spin Hall effect, and are generally soft and easily damaged by ion milling.

Therefore, there is a need for an improved SOT device design utilizing BiSb layer(s) having a desired crystal orientation and a high signal-to-noise ratio.

SUMMARY OF THE DISCLOSURE

The present disclosure generally relates to spin-orbit torque (SOT) devices comprising a bismuth antimony (BiSb) layer. The SOT devices further comprises a first shield, a BiSb layer disposed over the first shield, a free layer (FL) disposed over the BiSb layer, and a second shield disposed over the FL. The first shield, the FL, and the second shield are disposed at a media facing surface (MFS). The BiSb layer is recessed from the MFS a first distance of about 5 nm to about 20 nm. The FL has a length greater than the first distance. A notch and/or an insulation layer is disposed adjacent to the BiSb layer at the MFS. In one embodiment, current is configured to flow vertically through the second shield to the free layer, and horizontally from the FL to the BiSb layer. In another embodiment, current is configured to flow vertically through the second shield to the first shield.

In one embodiment, a magnetic recording head comprises a first shield extending to a media facing surface (MFS), a bismuth antimony (BiSb) layer disposed over the first shield, the BiSb layer being recessed from the MFS, a free layer disposed over the BiSb layer, the free layer extending to the MFS, and a second shield disposed over the free layer, the second shield extending to the MFS.

In another embodiment, a magnetic recording head comprises a first shield extending to a media facing surface (MFS), a first notch disposed on the first shield, the first notch having a first portion disposed at the MFS, a buffer layer disposed on the first notch, the buffer layer being recessed from the MFS, a bismuth antimony (BiSb) layer disposed on the buffer layer, the BiSb layer being recessed from the MFS, a free layer disposed over the BiSb layer, the free layer extending to the MFS, and a second shield disposed over the free layer, the second shield extending to the MFS.

In another embodiment, a magnetic recording head comprises a first shield extending to a media facing surface (MFS), a buffer layer disposed on the first shield, a bismuth antimony (BiSb) layer disposed on the buffer layer, the BiSb layer being recessed from the MFS a first distance of about 5 nm to about 20 nm, an interlayer disposed on the BiSb layer, a free layer disposed over the interlayer, the free layer extending to the MFS, wherein the free layer has a first length extending from the MFS greater than the first distance, a cap layer disposed over the free layer, and a second shield disposed over the cap layer, the second shield extending to the MFS.

DETAILED DESCRIPTION

The present disclosure generally relates to spin-orbit torque (SOT) devices comprising a bismuth antimony (BiSb) layer. The SOT devices further comprises a first shield, a BiSb layer disposed over the first shield, a free layer (FL) disposed over the BiSb layer, and a second shield disposed over the FL. The first shield, the FL, and the second shield are disposed at a media facing surface (MFS). The BiSb layer is recessed from the MFS a first distance of about 5 nm to about 20 nm. The FL has a length greater than the first distance. A notch and/or an insulation layer is disposed adjacent to the BiSb layer at the MFS. In one embodiment, current is configured to flow vertically through the second shield to the free layer, and horizontally from the FL to the BiSb layer. In another embodiment, current is configured to flow vertically through the second shield to the first shield.

A BiSb layer having a (012) orientation or a (001) orientation has a significant spin Hall angle and high electrical conductivity. Therefore, a BiSb layer having a (012) orientation or a (001) orientation can form a SOT device. For example, a BiSb layer having a (012) orientation or a (001) orientation can be used as a spin Hall layer in a spin-orbit torque device in a magnetic recording head, e.g., as part of a write head (MAMR). In another example, a BiSb layer having a (012) orientation or a (001) orientation can be used in nano oscillator devices for reading head applications where a signal is detected in the frequency domain. In another example, a BiSb layer having a (012) orientation or a (001) orientation can be used as a spin Hall electrode layer in an MRAM device. The SOT device can be in a perpendicular stack configuration or an in-plane stack configuration. The SOT device can be utilized in, for example, MAMR writing heads, read head, nano-oscillator based reader, MRAM, artificial intelligence chips, and other applications.

FIG.1is a schematic illustration of certain embodiments of a magnetic media drive100including a magnetic recording head having a SOT device. Such a magnetic media drive may be a single drive or comprise multiple drives. For the sake of illustration, a single disk drive100is shown according to certain embodiments. As shown, at least one rotatable magnetic disk112is supported on a spindle114and rotated by a drive motor118. The magnetic recording on each magnetic disk112is in the form of any suitable patterns of data tracks, such as annular patterns of concentric data tracks (not shown) on the magnetic disk112.

During operation of the disk drive100, the rotation of the magnetic disk112generates an air bearing between the slider113and the disk surface122which exerts an upward force or lift on the slider113. The air bearing thus counter-balances the slight spring force of suspension115and supports slider113off and slightly above the disk surface122by a small, substantially constant spacing during normal operation.

The above description of a typical magnetic media drive and the accompanying illustration ofFIG.1are for representation purposes only. It should be apparent that magnetic media drives may contain a large number of media, or disks, and actuators, and each actuator may support a number of sliders. It is to be understood that the embodiments discussed herein are applicable to a data storage device such as a hard disk drive (HDD) as well as a tape drive, such as those conforming to the LTO (Linear Tape Open) standards. As such, any reference in the detailed description to an HDD or tape drive is merely for exemplification purposes and is not intended to limit the disclosure unless explicitly claimed. For example, references to disk media in an HDD embodiment are provided as examples only, and can be substituted with tape media in a tape drive embodiment. Furthermore, reference to or claims directed to magnetic recording devices or data storage devices are intended to include at least both HDD and tape drive unless HDD or tape drive devices are explicitly claimed.

FIG.2is a fragmented, cross-sectional side view of certain embodiments of a read/write head200having a SOT device. It is noted while an SOT device is shown in both the read head and write head, this is for illustrative purposes only, and an SOT device may be independently integrated into either only the read head or only the write head in various embodiments, or in both the read head and the write head. The read/write head200faces a magnetic media112. The read/write head200may correspond to the magnetic head assembly121described inFIG.1. The read/write head200includes a media facing surface (MFS)212, such as a gas bearing surface, facing the disk112, a write head210, and a magnetic read head211. As shown inFIG.2, the magnetic media112moves past the write head210in the direction indicated by the arrow232and the read/write head200moves in the direction indicated by the arrow234.

In some embodiments, the magnetic read head211is a SOT read head that includes an SOT sensing element204located between reader shields S1and S2, where a first current source270is coupled to S1and S2via one or more lead connections to provide a current to the SOT sensing element204. In some embodiments, a lead connection may be coupled to a shield within the SOT sensing device. Voltage detection leads (not shown) are within the SOT sensing element204. The magnetic fields of the adjacent magnetized regions in the magnetic disk112are detectable by the SOT sensing element204as the recorded bits. In SOT sensing elements204comprising a BiSb layer, such as the SOT devices described inFIGS.4A-4C, current flows perpendicular to the film plane, and the signal is read out by measuring the voltage in the BiSb layer generated by the inverse spin Hall effect. The SOT device of various embodiments can be incorporated into the read head211.

The write head210includes a main pole220, a leading shield206, a trailing shield240, and a coil218that excites the main pole220, where a second current source271is coupled to the main pole220and the trailing shield240. The coil218may have a “pancake” structure which winds around a back-contact between the main pole220and the trailing shield240, instead of a “helical” structure shown inFIG.2. In one embodiment, the write head210is a perpendicular magnetic recording (PMR) write head. In other embodiments, the write head210may use energy assisted magnetic recording (EAMR) technologies such as microwave assisted magnetic recording (MAMR) and heat assisted magnetic recording (HAMR).

InFIG.2, optionally a spin orbital torque (SOT) device230is shown as part of the write head structure to enable a MAMR recording effect, in one embodiment. As noted above, while an SOT device is shown inFIG.2for both the read head and the write head, the SOT devices are not required to be implemented in both. For example, the write head may instead include other components to support HAMR in which case SOT device230may be absent. The SOT device230is formed in a gap254between the main pole220and the trailing shield240. The main pole220includes a trailing taper242and a leading taper244. The trailing taper242extends from a location recessed from the MFS212to the MFS212. The leading taper244extends from a location recessed from the MFS212to the MFS212. The trailing taper242and the leading taper244may have the same degree of taper, and the degree of taper is measured with respect to a longitudinal axis260of the main pole220. In some embodiments, the main pole220does not include the trailing taper242and the leading taper244. Instead, the main pole220includes a trailing side (not shown) and a leading side (not shown), and the trailing side and the leading side are substantially parallel. The main pole220may be a magnetic material, such as a FeCo alloy. The leading shield206and the trailing shield240may be a magnetic material, such as a NiFe alloy. In certain embodiments, the trailing shield240can include a trailing shield hot seed layer241. The trailing shield hot seed layer241can include a high moment sputter material, such as CoFe, CoFeNi, CoFeX, FeX, or FeXN, where X includes at least one of Rh, Al, Ta, Zr, Co, Fe, N, and Ti. In certain embodiments, the trailing shield240does not include a trailing shield hot seed layer.

In some embodiments, the read head211is a spin torque oscillator (STO) read head with an STO oscillator sensing element204located between shields S1and S2. The magnetic fields of the adjacent magnetized regions in the magnetic disk112are detectable by the STO sensing element204as the recorded bits. The STO sensing elements204comprise a BiSb layer, such as an SOT device ofFIGS.3A-7C. The STO reader may be operated in a 4-terminal or a 3-terminal configuration, with an out-of-plane current flowing inside the SOT structure while a sensing voltage is read out in the film plane. The SOT device of various embodiments can be incorporated into the read head211.

FIGS.3A-7Cillustrate various views of spin-orbit torque (SOT) devices300,400,500,600,700, according to various embodiments. Each SOT device300,400,500,600,700may individually be used in the magnetic recording head of the drive100ofFIG.1or other suitable magnetic media drives, such as the read head211and/or write head210ofFIG.2. Aspects of the SOT devices300,400,500,600,700may be used in combination with one another.

Furthermore, while the SOT devices300,400,500,600,700are referred to as SOT devices, the SOT devices300,400,500,600,700may function as spin torque oscillator (STO) devices. In some embodiments, when the SOT devices300,400,500,600,700are used in a write head, the current flows in-plane to the SOT layer or bismuth antimony (BiSb) layer310, and the ferromagnetic (FM) or free layer is oscillated by the SOT generated by the spin Hall effect in the BiSb layer310.

FIGS.3A-3Cillustrate various views of a SOT device300, according to one embodiment.FIG.3Aillustrates a cross-sectional or APEX view of the SOT device300,FIG.3Billustrates a downtrack cross-sectional view of the SOT device300, andFIG.3Cillustrates a media facing surface (MFS) view of the SOT device300. The downtrack cross-sectional view ofFIG.3Billustrates the top of the free layer314, but does not show the second shield318.

The SOT device300comprises a first shield (S1)302, an insulation layer304disposed on the first shield302, a buffer layer306disposed on the insulation layer304, a spin Hall effect (SHE) layer or BiSb layer310disposed on the buffer layer306, an interlayer308disposed on the SHE layer310, a ferromagnetic (FM) layer312disposed on the interlayer308, a free layer314disposed on the FM layer312, a cap layer316disposed on the free layer314, and a second shield (S2)318disposed on the cap layer316. The FM layer312is optional, and may be a part of the free layer314. The first shield302further comprises a S1notch320disposed at the MFS. The insulation layer304is disposed on the S1notch320at the MFS, and is further disposed behind the S1notch320recessed from the MFS, such that the insulation layer304has a Z-like shape. The S1notch320has a thickness in the y-direction of about 1 nm to about 5 nm. The SOT device300may comprise additional layers not shown, such as a seed layer and/or a barrier layer.

In the SOT device300, the buffer layer306, the SHE layer310, the interlayer308, and the FM layer312are recessed from the MFS by a portion of the insulation layer304and the S1notch320. The free layer314and the cap layer316are disposed at the MFS. The buffer layer306, the SHE layer310, the interlayer308, and the FM layer312are recessed from the MFS a distance322in the z-direction of about 5 nm to about 20 nm. The free layer314and the cap layer316each individually has a stripe height324in the z-direction of about 10 nm to about 30 nm. The distance322the buffer layer306, the SHE layer310, the interlayer308, and the FM layer312are recessed from the MFS is less than the stripe height324. The buffer layer306, the SHE layer310, the interlayer308, and the FM layer312may also have a stripe height in the z-direction of about 10 nm to about 100 nm.

Furthermore, due to the S1notch320, the shield-to-shield spacing of the SOT device300is reduced at the MFS, which narrows the read gap. The shield-to-shield spacing is the distance321from the second shield318to the S1notch320at the MFS, which includes the free layer314, the cap layer316, and the portion of the insulation layer304disposed at the MFS. The distance321is about 5 nm to about 20 nm.

The SHE layer310comprises BiSb, and may be referred to as a BiSb layer310, a SOT layer310, and/or a topological insulator (TI) layer310. The BiSb layer310may have a thickness in the y-direction of about 50 Å to about 200 Å. The BiSb layer310may comprise undoped BiSb or doped BiSbX, where the dopant is less than about 10%, and where X is extracted from elements which don't readily interact with either Bi or Sb, such as Cu, Ag, Ge, Mn, Ni, Co Mo, W, Sn, B, N, In, Te, Se, Y, Pt, Ti, N, or in alloy combinations with one or more of aforementioned elements, like CuAg, CuNi, CoCu, AgSn. The BiSb layer310may have a (012) crystal orientation or a (001) crystal orientation. The BiSb layer310may have a width in the z-direction that is greater than a width of the free layer314, like shown inFIG.3B.

The cap layer316may comprise nonmagnetic, high resistivity materials, such as: thin ceramic oxides or nitrides of TiN, SiN, and MgO; amorphous/nanocrystalline metals such as NiFeTa, NiTa, NiHf, NiFeHf, CoHf, CoFeHf, NiVVTa, NiFeW, NiW, WRe, beta-Ta, and beta-W; or nitrides, oxides, or borides of above-mentioned elements, compounds, and/or alloys such as NiTaN, NiFeTaN, NiVVTaN, NiWN, WReN, TaN, WN, TaOx, WOx, WB, HfB, NiHfB, NiFeHfB, CoHfB, and CoFeHfB, where x is a numeral. In some embodiments, lower atomic number (Z) materials are preferred in the cap layer316to reduce sputter intermixing with the FM layer312, but high Z alloys can be used, if used in combination with a migration barrier beneath, or if the high Z elements are used with a high resistive oxide, nitride, or boride. The cap layer316can comprise multilayer combinations of the above-mentioned materials, and the overall thickness of the cap layer316in the y-direction is less than or equal to about 100 Å (nominally about 15 Å to about 50 Å).

The FM layer312, which serves as a part of the free layer314, has a thickness of about 5 Å to about 15 Å in the y-direction, and may comprise NiFe, CoFe, NiFeX, CoFeX, FeX, or NiX, where X=Co, Ni, Cu, Si, Al, Mn, Ge, Ta, Hf, and B. The FM layer312may comprise any magnetic layer combination or alloy combination of these elements that can yield a low coercivity, negative magnetostrictive FM layer312or in multilayer combinations with other higher polarizing materials like Heusler alloys or high Ni containing alloy FM layers.

The free layer314may comprise CoFeB, Co, CoFe, NiFe, or a similar material as the FM layer312. The insulation layer304comprises an insulating material like SiN, or an oxide like MgO and can be used in combination with a Heusler alloy layer, and is adjacent to the BiSb layer to maintain texture and control Bi and Sb interdiffusion. The first and second shields302,318and the S1notch320may individually comprise a magnetic permeable and electrically conductive material selected from the group consisting of NiFe, CoFe, NiFeCo, alloys, and their combination, NiFe, NiFeCr, or other soft magnetic materials.

Each of the buffer layer306and the interlayer308comprises magnetic or nonmagnetic Heusler alloys, where the Heusler alloys may be full Heusler alloys (i.e., X2YZ) or half Heusler alloys (i.e., XYZ). Full X2YZ type Heusler alloys generally have L21, cF16, or C1b type structures with an a-axis between about 5.70 Å and about 6.20 Å, which perfectly matches to RuAl or CrMo texturing layer452. Half XYZ type Heusler alloys generally have a B2 type or Pm-3m type structure with a-axis between about 2.85 Å to about 3.10 Å. However, the type or structure may vary with respect to both half and full Heusler alloys. For instance, RuMnAl, RhMnAl, and Al2CuRh, have a Pm-3m structure, and Ni2MnAl and Mn2NiAl have cF16 structures while Al2NiMn has a B2 structure.

Moreover, in some embodiments, each of buffer layer306and the interlayer308comprises: (1) amorphous/nanocrystalline layers formed from Heusler alloys in combination with elements, or alloy layers that don't readily mix with the SOT or FM layers, or uniform alloys formed by co-sputtering Heusler alloys with other elements, or alloys which don't readily intermix with SOT or FM layer, or (2) polycrystalline Heusler alloys, which are epitaxial layers in the SOT device300. With respect to amorphous/nanocrystalline buffer layers306and the interlayers308, thin polycrystalline Heusler alloys (both magnetic and nonmagnetic, and full or half Heusler alloys) can be used when alloyed with other elements that don't readily mix with the BiSb layer310, such as Cu, Ag, Ge, Mn, Ni, Co Mo, W, Sn, B, Te, Se, Y, Pt, Ti, N, and In, or in alloy combinations with one or more of aforementioned elements, such as CuAg, CuNi, CoCu, AgSn.

With respect to polycrystalline Heusler alloys, thin layers of Heusler alloys, both magnetic and nonmagnetic, full or half Heusler alloys, can be used as the buffer layer306and the interlayer308in (100) textured layer SOT devices (SOT orientation in this scenario is (012)). Heusler alloys generally have higher resistivities then the FM layer312, and transport spin currents or yield high spin polarization, while providing and maintaining (100) growth. Heusler alloys further have excellent lattice matching capabilities to MgO tunnel barrier layers and to bcc FM alloys. (100) texturing layers, such as a texture layer, can be used to establish the (100) texture, and non-magnetic Heusler X2YZ or XYZ having cF16 (C1b, L21) or B2 structures can be used to transmit the texture to the BiSb layer310, which in turn grows a strong (012) texture for the BiSb layer310with an epitaxial bcc, B2, or C1b, cF16, L21 Heusler interlayer to produce a strong epitaxial (100) texture for the bcc or B2 FM layer312.

Other non-Heusler, nonmagnetic materials that could be used for one or more of the epitaxial buffer layer306and/or the interlayer308for epitaxial growth are: B2 or bcc materials, such as AIX, where X=V, Mn, Fe, Co, Ni, Ru, Rh, and Nobel metals Re, Os, Ir, Pt, Au, and Pd or in alloy combinations thereof; CrMo, where Mo is between about 20% to about 50%, CrMoTi, Cr, MoV, CrMoW; or CrXY, where X and Y are each individually selected from the group consisting of: Al, Ti, Mn, Co, Ni, Ru, Mo, Rh, W, and V.

In some embodiments, the buffer layer306and/or the interlayer308can each be formed from thin ceramic oxide or nitride layers like TiN, WN, SiN, and Al2O3, and MgO in combination with other high resistive nonmagnetic material layers. The top portion of a multilayer interlayer308(e.g., not in direct contact with the FM layer312) may also be comprise of high resistivity heavier metal amorphous or amorphous/nanocrystalline metals like NiFeTa, NiTa, NiHf, NiFeHf, CoHf, CoFeHf, NiVVTa, NiFeW, NiW, and WRe; nanocrystalline metals like beta-Ta and beta-W; or nitrides, oxides, or borides of the aforementioned elements or alloys like NiTaN, NiFeTaN, NiWTaN, NiWN, WReN, TaN, WN, TaOx, WOx, TaBx, WBx, HfBx, NiHfB, NiFeHfB, and CoHfB, where x is a numeral.

The bottom portion of the interlayer308can be an amorphous/nanocrystalline material formed from Heusler alloys or other magnetic alloy materials when combined with aforementioned non-interacting elements or alloy combinations of those elements. Higher resistivity nonmagnetic alloys which do not interact with the FM layer312, such as CuAg, CuNi, NiAg, CoCu, NiAl, RuAl, RhAl, and AgSn, can also be used for the interlayer308. The interlayer308can also be a polycrystalline nonmagnetic Heusler alloy or half Heusler alloy, or other B2 or bcc materials, such as AIX, where X=V, Mn, Fe, Co, Ni, Ru, Rh, and Nobel metals Re, Os, Ir, Pt, Au, and Pd or in alloy combinations thereof; CrMo, where Mo is between about 20% to about 50%, CrMoTi, Cr, MoV, CrMoW; or CrXY, where X and Y are each individually selected from the group consisting of: Al, Ti, Mn, Co, Ni, Ru, Mo, Rh, W, and V; or in any combination of these material layers which has a higher resistive non-interacting layer next to the FM layer312, among others.

When alloyed with nonmagnetic materials that do not readily intermix with FM layer312, examples of high resistive amorphous interlayers308materials include Ge/CoFe/CuAg (as used here “I” denotes separate sub-layers in a stack or layer) (where Ge/CoFe may form a single layer at room temperature or may be deposited as an alloy layer, and where Ge has a thickness of about 6 Å, CoFe has a thickness of about 4 Å, and CuAg has a thickness of about 3 Å), CuAg/Ge/CoFe/CuAg (where CuAg/Ge/CoFe may form a single layer at room temperature or may be deposited as an alloy layer, and where CuGe has a thickness of about 3 Å, Ge has a thickness of about 5 Å, CoFe has a thickness of about 4 Å, and CuAg has a thickness of about 2 Å), or thin nonmagnetic alloy layers like CoFeGe, NiFeGe, CoFeGeAg, etc. (alloy composition for alloys with Ge should be greater than about 44 at. % Ge to render the alloy nonmagnetic). When alloyed with nonmagnetic materials that do not readily intermix with FM layer312, additional examples of elements, compounds, or crystalline/amorphous/nanocrystalline materials that may be utilized as the interlayer308include: Ge/CoFe/NiFeTaN (where Ge/CoFe may form a single layer at room temperature or may be deposited as an alloy layer, and where Ge has a thickness of about 6 Å, CoFe has a thickness of about 4 Å, and NiFeTaN has a thickness of about 3 Å); Ge/CoFe/MgO (where Ge/CoFe may form a single layer at room temperature or may be deposited as an alloy layer, and where Ge has a thickness of about 6 Å, CoFe has a thickness of about 4 Å, and MgO has a thickness of about 3 Å); and MgO/Ge/CoFe (where Ge/CoFe may form a single layer at room temperature or may be deposited as an alloy layer, and where MgO has a thickness of about 3 Å, Ge has a thickness of about 6 Å, and CoFe has a thickness of about 4 Å). Examples of an interlayer308using alloys with X2YZ Heusler alloys would be Ge/Co2FeGe (which may form a single layer at room temperature or may be deposited as an alloy layer, and where Ge is about 4 Å thick and Co2FeGe is about 5 Å thick); or using alloys with XYZ half Heusler alloys like Ge/CoFeGe (which may form a single layer at room temperature or may be deposited as an alloy layer, where Ge is about 3 Å thick and CoFeGe is about 6 Å thick); and Ge/CoA (which may form a single layer at room temperature or may be deposited as an alloy layer), Ge/FeA (which may form a single layer at room temperature or may be deposited as an alloy layer), or Ge/NiA (which may form a single layer at room temperature or may be deposited as an alloy layer), where A can be one or more elements belonging to full Heusler alloys X2YZ or half Heusler alloys XYZ; or used in combination with very thin (i.e., dusting layers about 1 Å to about 5 Å thick) of nonmagnetic seed or capping layers of alloys of CuAg, NiCr, CoCu, AgSn, etc., such as Ge/X2YZ/CuAg, Ge/X2YZ/CuNi, CuN i/Ge/X2YZ, or CuAg/Ge/X2YZ/Cu Ni. The alloy composition should be nonmagnetic as in the case of alloys with one of the aforementioned non-interacting elements or alloys of these elements like Ge where Ge exceeds about 44 at. % to render the alloy nonmagnetic.

Additionally, the interlayer308may comprise nonmagnetic alloy or multilayer stack containing one or more of the following elements Cu, Ag, Ge, Mn, Ni, Co, Mo, W, In, B, Te, Se, Y, Pt, Ti, N, and Sn; or in conjunction with magnetic alloys such as CoA, FeA, and NiA, where A can be one or more elements belonging to full Heusler alloys X2YZ or half Heusler alloys XYZ, where X is selected from the group consisting of: Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au; where Y is selected from the group consisting of: Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Nb, Mo, Hf and W; and where Z is selected from the group consisting of: B, Al, S1, Ga, Ge, As, In, Sn, Sb, and Bi. The magnetic alloys or Heusler alloys should combine with other layers, combinations of elements, or other alloys to form a nonmagnetic layer or multilayer stack after room temperature deposition and intermixing, or deposited as a nonmagnetic single layer alloy, or in combinations thereof. The overall total thickness of the interlayer308is less than about 20 Å, such as about 3 Å to about 15 Å to ensure adequate magnetic coupling of the FM layer312to the BiSb layer310. Nonmagnetic polycrystalline Heusler alloys may also be used for the interlayer308, such as V2VAl or [Mn0.5Co0.5]2VAl, etc.

The interlayer308should have higher resistivity and be nonmagnetic. Thin, high resistivity, low Z ceramic oxide and nitride layers of TiN, SiN, Al2O3, MgO, thin layers can be used in the interlayer308. Furthermore, other materials that may be used as the interlayer308if not disposed in direct contact with the BiSb layer310include: high resistivity, heavier metal amorphous/nanocrystalline metals such as NiFeTa, NiTa, NiVVTa, NiFeW, NiW, and WRe; nanocrystalline metals like beta-Ta or beta-W; or nitrides, oxides, or borides of the aforementioned elements or alloys such as NiTaN, NiFeTaN, NiVVTaN, NiWN, WReN, TaN, WN, TaOx, WOx, TaBx, WBx, and HfBx. Higher resistivity, nonmagnetic alloys which don't readily interact with the BiSb layer310or the FM layer312may also be used for the interlayer308, such as Cu, Ag, Ge, Mn, Ni, Co Mo, W, Sn, B, In, and multi-element alloys combinations thereof, like CuAg, CuNi, NiAg, CoCu, NiAl, RuAl, RhAl, CuCo, and AgSn.

Examples of high resistive, amorphous materials for the interlayer308include Ge (6 Å)/CoFe (4 Å)/CuAg (3 Å) (which may form a single layer at room temperature or may be deposited as an alloy layer), CuAg (3 Å)/Ge (5 Å)/CoFe (3 Å)/CuAg (2 Å) (which may form a single layer at room temperature or may be deposited as an alloy layer), or single alloy nonmagnetic layers of CoFeGe, NiFeGe, CoFeGeAg, among others. The interlayer308may comprise thin multilayer stacks consisting of the aforementioned elements, compounds, or crystalline/amorphous/nanocrystalline layers as long as the overall multilayer stack is nonmagnetic and has a high resistivity.

Magnetic alloys and magnetic Heusler alloys can be used for the interlayer308if used in combinations with other elements or alloys above such that when deposited, the materials intermix at room temperature, or after post annealing, to form a nonmagnetic stack. Examples include layers of NiFeX, CoFeX, NiX, FeX, CoX, where X is an element that does not readily interact with BiSb, such as Cu, Ag, Ge, Mn, Ni, Co, Mo, W, Sn, B, Te, Se, Y, Pt, Ti, N, and In, or magnetic Heusler alloys deposited on non-interacting element or alloy layers like Ge layers and in single alloy deposition layers where the resulting Ge content in the intermixed alloy renders it nonmagnetic (e.g., in the case of alloying with Ge the Ge content should be greater than or equal to about 44 at. %); or in combination with sufficiently thick layers of elements which do not readily interact with BiSb, such as Cu, Ag, Ge, Mn, Ni, Co, Mo, W, Sn, B, and In, to form multi-element, nonmagnetic, high resistivity combinations thereof; or single polycrystalline nonmagnetic Heusler layers.

Another example of materials that may be used for the interlayer308and/or the buffer layer306include: Ge/CoFe/NiFeTaN (where Ge/CoFe may form a single layer at room temperature or may be deposited as an alloy layer, and where Ge has a thickness of about 6 Å, CoFe has a thickness of about 4 Å, and NiFeTaN has a thickness of about 3 Å).

The buffer layer306may further comprise any of the above-listed materials used in the interlayer308, such as a single alloy layer or layer combinations; nonmagnetic alloys or multilayer stacks comprising one or more of the following elements Cu, Ag, Ge, Mn, Ni, Mo, and W; or multi-element alloy combinations thereof; or in conjunction with magnetic and or nonmagnetic alloys such as CoA, FeA, NiA, where A is one or more elements belonging to full Heusler alloys X2YZ or half Heusler alloys XYZ, where X is selected from the group consisting of: Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au; Y is selected from the group consisting of: Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Nb, Mo, Hf, and W; and Z is selected from the group consisting of: B, Al, Si, Ga, Ge, As, In, Sn, Sb, and Bi. The magnetic alloy or Heusler alloys should combine with other elements such as Cu, Ag, Ge, Mn, Co, Ni, Mo, Sn, In, B, Te, Se, Y, Pt, Ti, N, and W, or combine in multi-elemental alloy layers thereof, to form a nonmagnetic total stack buffer layer306. The buffer layer306may be thin or relatively thick, such as having a thickness in the y-direction of about 5 Å to about 100 Å. A thicker buffer layer306can provide better migration resistance against elements from neighboring stacks getting into the BiSb layer310, or provide better migration resistance of the Bi or the Sb migration out of the BiSb layer310. The buffer layer306can be made thicker by lamination of layers to better control SOT nucleation/growth and texture.

Additional examples of materials that can be used for the buffer layer306include: [Ge/X2YZ]*n laminations, [Ge/XYZ]*n laminations, and [Ge/XYZ]*n laminations, where n is a whole numeral; Ge-enriched X2YZ and Ge-enriched XYZ single layer alloys such that the buffer layer306is nonmagnetic (i.e., Ge>44%); [Ge (6 Å)/Co2(MnFe)Ge (4 Å)]*4, [Ge (3 Å)/CoFeGe (6 Å)]*3, and [Ge (6 Å)/NiFe (4 Å)]*n; and with Ge alloyed or layered with NiA, FeA, CoA in lamination, where A is one or more elements belonging to full Heusler alloys X2YZ or half Heusler alloys XYZ, for example, [Ge (6 Å)/NiA (4 Å)]*n] where 1<n<4. The overall buffer layer306has a thickness between about 10 Å to about 50 Å.

As shown inFIGS.3B and3C, soft bias (SB) side shields326are disposed on either side of the free layer314at the MFS. The SB side shields326comprise a magnetic material, such as NiFe, CoFe, NiFeCo, CoFeHf, CoFeCr, or combinations thereof. The SB side shields326may be spaced from the free layer314and/or the insulation layer304by one or more insulation layers303. The insulation layers303may be part of the insulation layer304. For clarity, only the free layer314and the BiSb layer310are shown inFIG.3Band only the free layer314is shown inFIG.3C. However, the cap layer316and/or additional layers may be exposed at the MFS as well, as discussed above.

During operation, current (at the I+ lead) is applied or injected into the second shield318, such as by the current source270ofFIG.2. The current, which is spin-polarized when it comes out of the interlayer308, then flows down through the second shield318in the −y-direction through the cap layer316, the free layer314, the FM layer312, and the interlayer308. The current then flows perpendicular in the z-direction through the BiSb layer310, away from the MFS, to the back of the BiSb layer310as the current (at the I− lead) return path (shown by arrow350inFIG.3A). While flowing within the BiSb layer310, there will be transverse voltage induced by the spin current, due to an inverse spin Hall effect, which can be sensed or detected at the cross-track locations marked V+ and V−, shown inFIG.3B. The S1notch320and the insulation layer304disposed between the buffer layer306and the first shield302each help to confine the current path to be an L-like shape. Because the BiSb layer310is recessed from the MFS and the free layer314is exposed at the MFS, the field sensing of the voltage is improved.

FIGS.4A-4Cillustrate various views of a SOT device400, according to another embodiment.FIG.4Aillustrates a cross-sectional or APEX view of the SOT device400,FIG.4Billustrates a downtrack cross-sectional view of the SOT device400, andFIG.4Cillustrates a MFS view of the SOT device400. The downtrack cross-sectional view ofFIG.4Billustrates the top of the free layer314, but does not show the second shield318.

The SOT device400comprises a first shield (S1)402, a S1notch420disposed on the first shield402, an insulation layer404disposed on the first shield402excluding where the S1notch is disposed, the buffer layer306disposed on the recessed portion of the S1notch420, the BiSb layer310disposed on the buffer layer306, the interlayer308disposed on the BiSb layer310, the FM layer312disposed on the interlayer308, the free layer314disposed on the FM layer312, the cap layer316disposed on the free layer314, and the second shield (S2)318disposed on the cap layer316.

The S1notch420disposed at the MFS. The insulation layer404is disposed on the S1notch420at the MFS, and is further disposed between the S1notch420and a portion of the S1notch420recessed from the MFS. A portion of the insulation layer404may be disposed behind the recessed portion of the S1notch420. The S1notch420has a thickness in the y-direction of about 20 nm to about 100 nm. The first shield402and S1notch420each individually comprises a magnetic permeable and electrically conductive material selected from the group consisting of NiFe, CoFe, NiFeCo, or any material listed above for the first shield302ofFIGS.3A-3C. The S1notch420having a disposed at the MFS and a portion recessed from the MFS helps to confine the vertical current path, as discussed further below.

The SOT device400may comprise additional layers not shown, such as a seed layer and/or a barrier layer. The materials of each of the buffer layer306, the BiSb layer310, the interlayer308, the FM layer312, the free layer314, and the cap layer316are described above. The insulation layer404comprises an insulating material like SiN, AlOx, where x is a numeral, or an oxide like MgO and can be used in combination with a Heusler alloy layer, and is adjacent to the BiSb layer to maintain texture and control Bi and Sb interdiffusion

Similar to the SOT device300ofFIGS.3A-3C, in the SOT device400, the buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312are recessed from the MFS by a portion of the insulation layer404. The free layer314and the cap layer316are disposed at the MFS. The buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312are recessed from the MFS a distance322in the z-direction of about 5 nm to about 20 nm. The free layer314and the cap layer316each individually has a stripe height324in the z-direction of about 10 nm to about 30 nm. The distance322the buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312are recessed from the MFS is less than the stripe height324. The buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312may also have a stripe height in the z-direction of about 10 nm to about 50 nm.

Comparing the SOT device400to the SOT device300, in the SOT device400, the buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312are recessed from the MFS by a portion of the insulation layer404, rather than by the S1notch320and the insulation layer304like in the SOT device300. Additionally, the buffer layer306of the SOT device400is disposed on the S1notch420, rather than on the insulation layer304like in the SOT device300.

Furthermore, due to the S1notch420, the shield-to-shield spacing of the SOT device400is reduced, which narrows the read gap. The shield-to-shield spacing is the distance421from the second shield318to the S1notch420at the MFS, which includes the free layer314, the cap layer316, and the portion of the insulation layer404disposed at the MFS. The distance421is about 5 nm to about 20 nm.

As shown inFIGS.4B and4C, the SB side shields326are disposed on either side of the free layer314at the MFS. The SB side shields326may be spaced from the free layer314and/or the insulation layer404by one or more insulation layers303. The insulation layers303may be part of the insulation layer404. For clarity, only the free layer314and the BiSb layer are shown inFIG.4Band only the free layer314is shown inFIG.4C. However, the cap layer316and/or additional layers may be exposed at the MFS as well, as discussed above.

During operation, current (at the 1+ lead) is applied or injected into the second shield318, such as by the current source270ofFIG.2. The current then flows down through the second shield318in the −y-direction through the cap layer316, the free layer314, the FM layer312, the interlayer308, the BiSb layer310, the buffer layer306, the S1notch420, and the first shield402as the current (at the I− lead) return path, as shown by arrow450inFIG.4A. The current, which is spin-polarized when it comes out of the interlayer308, will induce a transverse voltage inside the BiSb layer310along cross-track direction, due to the inverse spin Hall effect. This induced voltage, which varies dependent on the free layer314's orientation responsive to sensed magnetic field from the media, is sensed or detected at the locations marked V+ and V−, shown inFIG.4B. The S1notch420having a disposed at the MFS and a portion recessed from the MFS helps to confine the vertical current path. Because the BiSb layer310is recessed from the MFS and the free layer314is exposed at the MFS, the field sensing of the voltage is improved.

FIGS.5A-5Cillustrate various views of a SOT device500, according to yet another embodiment.FIG.5Aillustrates a cross-sectional or APEX view of the SOT device500,FIG.5Billustrates a downtrack cross-sectional view of the SOT device500, andFIG.5Cillustrates a MFS view of the SOT device500. The downtrack cross-sectional view ofFIG.5Billustrates the top of the free layer314, but does not show the second shield518or the S2notch528.

The SOT device500comprises the first shield (S1)402, the S1notch420disposed on the first shield402, the insulation layer404disposed adjacent to the S1notch420, the buffer layer306disposed on the S1notch402, the BiSb layer310disposed on the buffer layer306, the interlayer308disposed on the BiSb layer310, the FM layer312disposed on the interlayer308, the free layer314disposed on the FM layer312, the cap layer316disposed on the free layer314, and a second shield (S2)518disposed on the cap layer316. The insulation layer404is disposed on the S1notch420at the MFS, and is further disposed between the S1notch420and a portion of the S1notch420recessed from the MFS. A portion of the insulation layer404may be disposed behind the recessed portion of the S1notch420. The second shield518further comprises a S2notch528. The S2notch528is disposed between and in contact with the second shield518and the cap layer316at the MFS. The S2notch528may have a thickness in the y-direction of about 3 nm to about 20 nm. The second shield518and the S2notch528each individually comprises a magnetic permeable and electrically conductive material selected from the group consisting of NiFe, CoFe, NiFeCo, NiFe, CoFe, NiFeCr, or other soft magnetic shielding materials.

The SOT device500may comprise additional layers not shown, such as a seed layer and/or a barrier layer. The materials of each of the buffer layer306, the BiSb layer310, the interlayer308, the FM layer312, the free layer314, the cap layer316, and the insulation layer404are described above.

Similar to the SOT device400ofFIGS.4A-4C, in the SOT device500, the buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312are recessed from the MFS by a portion of the insulation layer404. The free layer314and the cap layer316are disposed at the MFS. The buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312are recessed from the MFS a distance322in the z-direction of about 5 nm to about 20 nm. The free layer314and the cap layer316each individually has a stripe height324in the z-direction of about 10 nm to about 20 nm. The distance322the buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312are recessed from the MFS is less than the stripe height324. The buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312may also have a stripe height in the z-direction of about 10 nm to about 20 nm.

Furthermore, due to the S1notch420and the S2notch528, the shield-to-shield spacing of the SOT device500is reduced, which narrows the read gap. The shield-to-shield spacing is the distance521from the S2notch528to the S1notch420at the MFS, which includes the free layer314, the cap layer316, and the portion of the insulation layer404disposed at the MFS. The distance521is about 5 nm to about 20 nm.

As shown inFIGS.5B and5C, the SB side shields326are disposed on either side of the free layer314at the MFS. The SB side shields326may be spaced from the free layer314and/or the insulation layer404by one or more insulation layers303. The insulation layers303may be part of the insulation layer404. A width of the S1notch420at the MFS in the x-direction may be equal to or greater than a width of the free layer314. For clarity, only the free layer314and the BiSb layer310are shown inFIG.5Band only the free layer314is shown inFIG.5C. However, the cap layer316and/or additional layers may be exposed at the MFS as well, as discussed above.

The SOT device500further comprises an anti-ferromagnetic (AFM) layer534disposed on the SB side shields326and adjacent to the S2notch528. An insulation layer532is disposed on the AFM layer534and adjacent to the S2notch528. The AFM layer534pins the SB side shields326. The AFM layer534may comprise a single or multiple layers of PtMn, NiMn, IrMn, IrMnCr, CrMnPt, FeMn, other antiferromagnetic materials, or combinations thereof.

During operation, current (at the I+ lead) is applied or injected into the second shield518, such as by the current source270ofFIG.2. The current then flows down through the second shield518in the −y-direction through the S2notch528, the cap layer316, the free layer314, the FM layer312, the interlayer308, the BiSb layer310, the buffer layer306, the S1notch420, and the first shield402as the current (at the I− lead) return path, as shown by arrow550inFIG.5A. The current, which is spin-polarized when it comes out of the interlayer308, will induce a transverse voltage inside the BiSb layer310along cross-track direction, due to the inverse spin Hall effect. This induced voltage, which varies dependent on the free layer314's orientation responsive to sensed magnetic field from the media, is sensed or detected at the locations marked V+ and V−, shown inFIG.5B. The S1notch420and the S2notch528each help to confine the vertical current path. Because the BiSb layer310is recessed from the MFS and the free layer314is exposed at the MFS, the field sensing of the voltage is improved.

Comparing the SOT device500to the SOT device400, in the SOT device500comprises the S2notch528, whereas the second shield318of the SOT device400does not. Additionally, the SOT device500further comprises the AFM layer534and the insulation layer532, whereas the SOT device400does not.

FIGS.6A-6Cillustrate various views of a SOT device600, according to another embodiment.FIG.6Aillustrates a cross-sectional or APEX view of the SOT device600,FIG.6Billustrates a downtrack cross-sectional view of the SOT device600, andFIG.6Cillustrates a MFS view of the SOT device600. The downtrack cross-sectional view ofFIG.6Billustrates the top of the free layer314, but does not show the second shield518or the S2notch528.

The SOT device600comprises a first shield (S1)602, the S1notch620disposed on the first shield602, the insulation layer604disposed on the S1notch620, the buffer layer306disposed on the first shield602, the BiSb layer310disposed on the buffer layer306, the interlayer308disposed on the BiSb layer310, the FM layer312disposed on the interlayer308, the free layer314disposed on the FM layer312, the cap layer316disposed on the free layer314, and the second shield (S2)518disposed on the cap layer316. The insulation layer604is disposed on the S1notch620at the MFS, and is further disposed behind the S1notch620recessed from the MFS (e.g., between the S1notch620and the buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312). The second shield518further comprises the S2notch528. The S2notch528is disposed between and in contact with the second shield518and the cap layer316at the MFS. The S1notch620and the first shield602each individually comprises a magnetic permeable and electrically conductive material selected from the group consisting of NiFe, CoFe, NiFeCo, or any material listed above for the first shield302inFIGS.3A-3C. The S1notch620has a thickness in the y-direction of about 1 nm to about 5 nm.

The SOT device600may comprise additional layers not shown, such as a seed layer and/or a barrier layer. The materials of each of the buffer layer306, the BiSb layer310, the interlayer308, the FM layer312, the free layer314, and the cap layer316. The insulation layer604comprises an insulating material like SiN, AlOx, where x is a numeral, or an oxide like MgO and can be used in combination with a Heusler alloy layer, and is adjacent to the BiSb layer to maintain texture and control Bi and Sb interdiffusion

Similar to the SOT device500ofFIGS.5A-5C, in the SOT device600, the buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312are recessed from the MFS by a portion of the insulation layer604. The free layer314and the cap layer316are disposed at the MFS. The buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312are recessed from the MFS a distance322in the z-direction of about 5 nm to about 20 nm. The free layer314and the cap layer316each individually has a stripe height324in the z-direction of about 10 nm to about 20 nm. The distance322the buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312are recessed from the MFS is less than the stripe height324. The buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312may also have a stripe height in the z-direction of about 10 nm to about 20 nm.

Furthermore, due to the S1notch620and the S2notch528, the shield-to-shield spacing of the SOT device600is reduced, which narrows the read gap. The shield-to-shield spacing is the distance621from the S2notch528to the S1notch620at the MFS, which includes the free layer314, the cap layer316, and the portion of the insulation layer604disposed at the MFS. The distance621is about 5 nm to about 20 nm.

As shown inFIGS.6B and6C, the SB side shields326are disposed on either side of the free layer314at the MFS, and may be spaced from the free layer314by an insulation layer (not shown). The SB side shields326are disposed in contact with the first shield602and the insulation layer604. Since the insulation layer604surrounds the S1notch620at the MFS, the SB side shields326are spaced from the S1notch620. The SOT device600further comprises the insulation layer532disposed on the SB side shields326and adjacent to the S2notch528. For clarity, only the free layer314and the BiSb layer310are shown inFIG.6Band only the free layer314is shown inFIG.6C. However, the cap layer316and/or additional layers may be exposed at the MFS as well, as discussed above.

During operation, current (at the I+ lead) is applied or injected into the second shield518, such as by the current source270ofFIG.2. The current then flows down through the second shield518in the −y-direction through the S2notch528, the cap layer316, the free layer314, the FM layer312, the interlayer308, the BiSb layer310, the buffer layer306, and the first shield602as the current (at the I− lead) return path, as shown by arrow650inFIG.6A. The current, which is spin-polarized when it comes out of the interlayer308, will induce a transverse voltage inside the BiSb layer310along cross-track direction, due to the inverse spin Hall effect. This induced voltage, which varies dependent on the free layer314's orientation responsive to sensed magnetic field from the media, is sensed or detected at the locations marked V+ and V−, shown inFIG.6B. The S1notch620and the S2notch528each helps to confine the vertical current path. Because the BiSb layer310is recessed from the MFS and the free layer314is exposed at the MFS, the field sensing of the voltage is improved.

Comparing the SOT device600to the SOT device500, in the SOT device600, the buffer layer306is disposed in contact with the first shield602, whereas the buffer layer306of the SOT device500is disposed in contact with the S1notch420. Additionally, the SOT device600does not comprise the AFM layer534on the insulation layer532.

FIGS.7A-7Cillustrate various views of a SOT device700, according to yet another embodiment.FIG.7Aillustrates a cross-sectional or APEX view of the SOT device700,FIG.7Billustrates a downtrack cross-sectional view of the SOT device700, andFIG.7Cillustrates a MFS view of the SOT device700. The downtrack cross-sectional view ofFIG.7Billustrates the top of the free layer314, but does not show the second shield518or the S2notch528.

The SOT device700comprises a first shield (S1)702, a S1notch720disposed on the first shield702, the insulation layer704disposed on the S1notch720and on the first shield702, the buffer layer306disposed on the insulation layer704, the BiSb layer310disposed on the buffer layer306, the interlayer308disposed on the BiSb layer310, the FM layer312disposed on the interlayer308, the free layer314disposed on the FM layer312, the cap layer316disposed on the free layer314, the S2notch528disposed on the cap layer316, and the second shield (S2)518disposed on the S2notch528. The insulation layer704is disposed on the S1notch720at the MFS, and is further disposed behind the S1notch720recessed from the MFS and between the first shield702and the buffer layer306such that the insulation layer704has a Z-like shape. The second shield518further comprises the S2notch528. The S2notch528is disposed between and in contact with the second shield518and the cap layer316at the MFS. The S1notch720, the first shield702, the S2notch528, and the second shield518each individually comprises a magnetic permeable and electrically conductive material selected from the group consisting of NiFe, CoFe, NiFeCo, or any material listed above for the first shield302inFIGS.3A-3C. The S1notch720has a thickness in the y-direction of about 1 nm to about 5 nm.

The SOT device700may comprise additional layers not shown, such as a seed layer and/or a barrier layer. The materials of each of the buffer layer306, the BiSb layer310, the interlayer308, the FM layer312, the free layer314, and the cap layer316are described above. The insulation layer704comprises an insulating material like SiN, AlOx, where x is a numeral, or an oxide like MgO and can be used in combination with a Heusler alloy layer, and is adjacent to the BiSb layer to maintain texture and control Bi and Sb interdiffusion

Similar to the SOT device300ofFIGS.3A-3C, in the SOT device700, the buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312are recessed from the MFS by a portion of the insulation layer704. The free layer314and the cap layer316are disposed at the MFS. The buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312are recessed from the MFS a distance322in the z-direction of about 5 nm to about 20 nm. The free layer314and the cap layer316each individually has a stripe height324in the z-direction of about 10 nm to about 20 nm. The distance322the buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312are recessed from the MFS is less than the stripe height324. The buffer layer306, the BiSb layer310, the interlayer308, and the FM layer312may also have a stripe height in the z-direction of about 10 nm to about 20 nm.

Furthermore, due to the S1notch720and the S2notch528, the shield-to-shield spacing of the SOT device700is reduced, which narrows the read gap. The shield-to-shield spacing is the distance721from the S2notch528to the S1notch720at the MFS, which includes the free layer314, the cap layer316, and the portion of the insulation layer704disposed at the MFS. The distance721is about 5 nm to about 20 nm.

As shown inFIGS.7B and7C, the SB side shields326are disposed on either side of the free layer314at the MFS, and may be spaced from the free layer314by an insulation layer (not shown). The SB side shields326are disposed in contact with the first shield702and the insulation layer704. Since the insulation layer704surrounds the S1notch720at the MFS, the SB side shields326are spaced from the S1notch720. The SOT device700further comprises the insulation layer532disposed on the SB side shields326and adjacent to the S2notch528. A width of the insulation layer532at the MFS in the x-direction is equal to or greater than a width of the SB side shields326. For clarity, only the free layer314and the BiSb layer310are shown inFIG.7Band only the free layer314is shown inFIG.7C. However, the cap layer316and/or additional layers may be exposed at the MFS as well, as discussed above.

During operation, current (at the I+ lead) is applied or injected into the second shield518, such as by the current source270ofFIG.2. The current then flows down through the second shield518in the −y-direction through S2notch528, the cap layer316, the free layer314, the FM layer312, and the interlayer308. The current then flows perpendicular in the z-direction through the BiSb layer310, away from the MFS, to the back of the BiSb layer310as the current (I−) return path (shown by arrow750inFIG.7A). The current, which is spin-polarized when it comes out of the interlayer308, will induce a transverse voltage inside the BiSb layer310along cross-track direction, due to the inverse spin Hall effect. This induced voltage, which varies dependent on the free layer314's orientation responsive to sensed magnetic field from the media, is sensed or detected at the locations marked V+ and V−, shown inFIG.7B. The I− lead is also shown inFIG.7Bat the top of the BiSb layer310. The S1notch720, the S2notch528, and the insulation layer704disposed between the buffer layer306and the first shield702all help to confine the current path to be an L-like shape. Because the BiSb layer310is recessed from the MFS and the free layer314is exposed at the MFS, the field sensing of the voltage is improved.

Comparing the SOT device700to the SOT device300, in the SOT device700, the SOT device700comprises the S2notch528, whereas the SOT device300does not, and the SB side shields326are in direct contact with the first shield702.

Therefore, by having a free layer of a SOT device disposed at the MFS while recessing a BiSb layer away from the MFS, the shield-to-shield spacing of the SOT device is reduced, which in turn, improves down-track resolution of the read gap of the SOT device. Furthermore, because the BiSb layer is recessed from the MFS and the free layer is exposed at the MFS, the field sensing of the current is improved during operation, improving the signal-to-noise ratio and the positioning of the SOT device.

In one embodiment, a magnetic recording head comprises a first shield extending to a media facing surface (MFS), a bismuth antimony (BiSb) layer disposed over the first shield, the BiSb layer being recessed from the MFS, a free layer disposed over the BiSb layer, the free layer extending to the MFS, and a second shield disposed over the free layer, the second shield extending to the MFS.

The magnetic recording head comprises a first notch disposed on the first shield at the MFS, wherein the BiSb layer is disposed adjacent to the first notch, and an insulation layer disposed on the first notch at the MFS, the insulation layer being in contact with the free layer. The magnetic recording head further comprises a buffer layer disposed between the first shield and the BiSb layer, the buffer layer being recessed from the MFS, an interlayer disposed over the BiSb layer, the interlayer being recessed from the MFS, and a cap layer disposed between the free layer and the second shield, the cap layer extending to the MFS. The insulation layer extends perpendicular from the MFS into the magnetic recording head, wherein the insulation layer is disposed between the buffer layer and the first shield, and wherein the insulation layer is disposed in contact with the buffer layer, the BiSb layer, and the interlayer. The magnetic recording head further comprises a second notch disposed in contact with the cap layer and the second shield, the second notch being disposed at the MFS. The BiSb layer is recessed a distance of about 5 nm to about 20 nm from the MFS. The free layer has a length extending from the MFS into the magnetic recording head greater than a distance the BiSb layer is recessed from the MFS. The magnetic recording head further comprises means for flowing a current vertically through the second shield into the free layer and horizontally out through the BiSb layer. A magnetic recording device comprising the magnetic recording head.

In another embodiment, a magnetic recording head comprises a first shield extending to a media facing surface (MFS), a first notch disposed on the first shield, the first notch having a first portion disposed at the MFS, a buffer layer disposed on the first notch, the buffer layer being recessed from the MFS, a bismuth antimony (BiSb) layer disposed on the buffer layer, the BiSb layer being recessed from the MFS, a free layer disposed over the BiSb layer, the free layer extending to the MFS, and a second shield disposed over the free layer, the second shield extending to the MFS.

The magnetic recording head further comprises an insulation layer disposed on the first notch at the MFS, the insulation layer being disposed adjacent to and in contact with the buffer layer and the BiSb layer. The buffer layer and the BiSb layer are recessed a first distance from the MFS, and a first length of the insulation layer is equal to the first distance. A second length of the free layer is greater than the first length. The magnetic recording head further comprises an interlayer disposed on the BiSb layer, and a cap layer disposed between the free layer and the second shield, the cap layer extending to the MFS. The magnetic recording head further comprises a second notch disposed between the second shield and the free layer, the second notch extending to the MFS, wherein a shield-to-shield spacing of the magnetic recording head is a second distance between the first notch and the second notch. The magnetic recording head further comprises means for flowing a current vertically through the second shield, the free layer, the BiSb layer, and the buffer layer to the first shield. The magnetic recording head further comprises a ferromagnetic (FM) layer disposed over the interlayer. A magnetic recording device comprising the magnetic recording head.

In another embodiment, a magnetic recording head comprises a first shield extending to a media facing surface (MFS), a buffer layer disposed on the first shield, a bismuth antimony (BiSb) layer disposed on the buffer layer, the BiSb layer being recessed from the MFS a first distance of about 5 nm to about 20 nm, an interlayer disposed on the BiSb layer, a free layer disposed over the interlayer, the free layer extending to the MFS, wherein the free layer has a first length extending from the MFS greater than the first distance, a cap layer disposed over the free layer, and a second shield disposed over the cap layer, the second shield extending to the MFS.

The buffer layer and the interlayer are recessed the first distance from the MFS. The magnetic recording head further comprises a first notch disposed on the first shield, the first notch being disposed at the MFS, and an insulation layer disposed on the first notch, the insulation layer being disposed in contact with the buffer layer, the BiSb layer, the interlayer, and the free layer. The magnetic recording head further comprises a second notch disposed between and in contact with the second shield and the cap layer. The magnetic recording head further comprises means for flowing a current vertically through the second shield, the cap layer, the free layer, the interlayer, the BiSb layer, and the buffer layer to the first shield. The magnetic recording head further comprises a ferromagnetic (FM) layer disposed between the interlayer and the free layer. A magnetic recording device comprising the magnetic recording head.