Headway Technologies, Incorporated

Shohei Kawasaki

Wenyu Chen

Yan Wu

Tetsuya Roppongi

Kunliang Zhang

Min Li

Glen A Garfunkel

Yuhui Tang

Ying Liu

Zheng Gao

Hui-Chuan Wang

Sangmun Oh

Zhenyao Tang

The present embodiments relate to write heads implementing microwave-assisted magnetic recording utilizing multiple spin torque oscillators (STOs). Each STO can include a field-generation layer (FGL) that can oscillate in a same frequency and out of phase with one another. The layers in each STO can enable mutual spin transfer torques between adjacent layers, which can drive the FGLs into a large angle oscillation. The oscillation between the FGLs can cause a magnetic field to be generated that can assist in writing to a magnetic recording medium.

Dual-spin torque oscillator designs in microwave assisted magnetic recording

The present embodiments relate to a tunnel magnetoresistance (TMR) element. The TMR element can include a free layer comprising a metallic alloy that is doped using a dopant element. In some instances, the metallic alloy comprises a cobalt-iron (CoFe) alloy. The present embodiments relate to doping a small amount of an element (e.g., hafnium (Hf), tantalum (Ta), Yttrium (Y)) in a high flux CoFe layer of a tunnel magnetoresistance (TMR) element. The small amount of dopant can suppress a long-range order in the CoFe film. The amorphous state of a CoFe alloy can be induced by the dopant and result in a magnetically soft layer. A resistance of the TMR element can be modified based on an application of an external magnetic field to the free layer and the pin layer.

Tunneling magnetoresistance device with magnetically soft high moment free layer

A read head includes a permanent magnet (PM) layer formed up to 100 nm behind a free layer where PM layer magnetization may be initialized in a direction that adjusts free layer (FL) bias point, and shifts sensor asymmetry (Asym) closer to 0% for individual heads at slider or Head Gimbal Assembly level to provide a significant improvement in device yield. Asym is adjusted using different initialization schemes and initialization directions. With individual heads, initialization direction is selected based on a prior measurement of asymmetry. The PM layer is CoPt or CoCrPt and has coercivity from 500 Oersted to 1000 Oersted. The PM layer may have a width equal to the FL, or in another embodiment, the PM layer adjoins a backside of the top shield and has a width equal to or greater than that of the FL.

Adaptive bias control for magnetic recording head

A STRAMR structure is disclosed. The STRAMR structure can include a spin torque oscillator (STO) device in a WG provided between the mail pole (MP) trailing side and a trailing shield. The STO device, includes: a flux guiding layer that has a negative spin polarization (nFGL) with a magnetization pointing substantially parallel to the WG field without the current bias and formed between a first spin polarization preserving layer (ppL1) and a second spin polarization preserving layer (ppL2); a positive spin polarization (pSP) layer that adjoins the TS bottom surface; a non-spin polarization preserving layer (pxL) contacting the MP trailing side; a first negative spin injection layer (nSIL1) between the ppL2 and a third spin polarization preserving layer (ppL3); and a second negative spin injection layer (nSIL2) between the ppL3 and the pxL, wherein the nFGL, nSIL1, and nSIL2 have a spin polarization that is negative.

Magnetic flux guiding device with spin torque oscillator (STO) film having negative spin polarization layers in assisted writing application

A method of forming a spin transfer torque reversal assisted magnetic recording (STRAMR) writer is disclosed wherein a spin torque oscillator (STO) has a flux guiding layer (FGL) wherein magnetization flips to a direction substantially opposing the write gap (WG) field when sufficient current (I) density is applied across the STO between a trailing shield and main pole (MP) thereby enhancing the MP write field. The FGL has a center portion with a larger magnetization saturation&#xd7;thickness (MsT) than in FGL outer portions proximate to STO sidewalls. Accordingly, lower Idensity is necessary to provide a given amount of FGL magnetization flipping and there is reduced write bubble fringing compared with writers having a FGL with uniform MsT. Lower MsT is achieved by partially oxidizing FGL outer portions. In some embodiments, there is a gradient in outer FGL portions where MsT increases with increasing distance from FGL sidewalls.

Writer with laterally graded spin layer MsT

A read head includes a permanent magnet (PM) layer formed up to 100 nm behind a free layer where PM layer magnetization may be initialized in a direction that adjusts free layer (FL) bias point, and shifts sensor asymmetry (Asym) closer to 0% for individual heads at slider or Head Gimbal Assembly level to provide a significant improvement in device yield. Asym is adjusted using different initialization schemes and initialization directions. With individual heads, initialization direction is selected based on a prior measurement of asymmetry. The PM layer is CoPt or CoCrPt and has coercivity from 500 Oersted to 1000 Oersted. The PM layer may have a width equal to the FL, or a width equal to the cross-track distance between outer sides of the longitudinal bias layers. In another embodiment, the PM layer adjoins a backside of the top shield.

A spin transfer torque reversal assisted magnetic recording (STRAMR) writer is disclosed wherein a spin torque oscillator has a flux guiding layer (FGL) wherein magnetization flips to a direction substantially opposing the write gap (WG) field when sufficient current (I) density is applied across the STO between a trailing shield and main pole (MP) thereby enhancing the MP write field. A key feature is that the FGL has a center portion with a larger magnetization saturation&#xd7;thickness (MsT) than in FGL outer portions proximate to STO sidewalls. Accordingly, lower Idensity is necessary to provide a given amount of FGL magnetization flipping and there is reduced write bubble fringing compared with writers having a FGL with uniform MsT. Lower MsT is achieved by partially oxidizing FGL outer portions. In some embodiments, there is a gradient in outer FGL portions where MsT increases with increasing distance from FGL sidewalls.

A spin transfer torque reversal assisted magnetic recording (STRAMR) structure is disclosed wherein two flux change layers (FCL1 and FCL2) are formed within a write gap (WG) and between a main pole (MP) trailing side and trailing shield (TS). Each FCL has a magnetization that flips to a direction substantially opposing a WG field when a direct current of sufficient current density is applied across the STRAMR device thereby increasing reluctance in the WG and producing a larger write field output at the air bearing surface. A reference layer (RL1) is used to reflect spin polarized electrons that exert spin torque on FCL1 and cause FCL1 magnetization to flip. A second reference layer (or the MP or TS) is employed to reflect spin polarize electrons that generate spin torque on FCL2 and flip FCL2 magnetization. Non-spin polarization preserving layers and spin polarization preserving layers are also in the STRAMR structure.

Dual flux change layer (FCL) assisted magnetic recording

A spin transfer torque reversal assisted magnetic recording (STRAMR) device is disclosed wherein a flux guiding layer (FGL) magnetization flips to an opposite direction opposing the write gap (WG) field because of spin torque from an adjacent spin polarization (SP) layer and spin injection layer (SIL) when a current (Ia) of sufficient density is applied across the device and between the main pole (MP) and trailing shield (TS) thereby enhancing the MP write field. The SP layer adjoins the MP or TS and maintains a magnetization in the WG field direction. One or both of the SIL and FGL has a spin polarization from &#x2212;0.4 to 0.3 and may be doped with C, N, or B so that the extent of FGL flipping is greater at a given current density than in the prior art where all magnetic layers within the STRAMR device have a positive spin polarization &#x2265;0.4.

Magnetic flux guiding device with spin torque oscillator (STO) film having one or more negative spin polarization layers in assisted writing application

A spin torque transfer (STT) assisted magnetic recording structure is disclosed wherein a magnetic flux guiding (MFG) device is formed between a main pole (MP) trailing side and a trailing shield (TS). The MFG device has a field generation layer (FGL) separated from first and second spin polarization (SP) layers by first and second non-magnetic layers, respectively. First and second SP layers have magnetizations in opposite directions so that when a direct current of sufficient magnitude is applied from the MP to TS, or from the TS to MP in other embodiments, FGL magnetization flips to a direction toward the MP and opposes a write gap field flux thereby enhancing the write field. Additive torque from two SP layers on the FGL enables lower current density for FGL flipping or a greater degree of FGL flipping at a given current density compared with MFG schemes having a single SP layer.

Magnetic flux guiding device with antiferromagnetically coupled (AFC) spin polarizer in assisted writing application

A spin torque transfer (STO) assisted magnetic recording structure is disclosed wherein a STO device has capability to generate a radio frequency (RF) field on a magnetic bit to lower the required write field during a write process. The STO device contains a field generation layer (FGL) with a magnetization that flips to a direction opposite to the write gap field when a current of sufficient current density is applied thereby increasing reluctance in the write gap and causing a larger write field output at the air bearing surface. A key feature is that a single spin polarization (SP) layer and an antiferromagnetically coupled SP layer comprised of SP1 and SP2 layers are formed on opposite sides of the FGL. SP1 magnetization is greater than SP2 magnetization. Additive torque from SP and SP2 layers on the FGL enables FGL flipping while SP1 and SP2 precessional states provide the RF field.

Growing community of inventors

Sunnyvale, CA, United States of America

Shohei Kawasaki