Magnetic flux guiding device with spin torque oscillator (STO) film having negative spin polarization layers in assisted writing application
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 (ppL 1 ) and a second spin polarization preserving layer (ppL 2 ); 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 (nSIL 1 ) between the ppL 2 and a third spin polarization preserving layer (ppL 3 ); and a second negative spin injection layer (nSIL 2 ) between the ppL 3 and the pxL, wherein the nFGL, nSIL 1 , and nSIL 2 have a spin polarization that is negative.
1 . A device comprising:
a main pole (MP) that is configured to generate a write field which is directed through a pole tip at an air bearing surface (ABS), and to generate a write gap (WG) field in a down-track direction across a spin torque oscillator (STO) device in a WG, and between a MP trailing side and a trailing shield (TS);
the trailing shield (TS) with a side at the ABS, and a bottom surface facing the MP; and
the STO device, comprising:
a first spin polarization preserving layer (ppL 1 ) disposed adjacent to a positive spin polarization (pSP) layer and a flux guiding layer (nFGL) that has a negative spin polarization, wherein the pSP layer is adjacent to the MP;
a second spin polarization preserving layer (ppL 2 ) disposed adjacent to the nFGL and a first negative spin injection layer (nSIL 1 ); and
a third spin polarization preserving layer (ppL 3 ) disposed adjacent to the nSIL 1 and a second negative spin injection layer (nSIL 2 ), wherein the nSIL 1 is in contact with both the ppL 2 and ppL 3 , and wherein the nSIL 2 is disposed adjacent to a non-spin polarization preserving layer (pxL) contacting the TS, wherein a magnetization of the nFGL is configured to flip to a direction substantially antiparallel to the WG field in response to a current of sufficient current density (J) being applied from the TS to the MP across the STO device, and wherein the nSIL 1 and nSIL 2 are configured to exert an additive spin torque on the nFGL to cause a magnetization of the nFGL to flip to a direction substantially antiparallel to the WG field, wherein the nSIL 1 and nSIL 2 exerting the additive spin torque on the nFGL increases a reluctance in the WG and enhances the write field, and wherein the nSIL 1 and nSIL 2 have a saturation magnetization x thickness (Mst) product substantially less than that of the nFGL.
2 . The device of claim 1 , wherein the nFGL comprises a magnetization pointing substantially parallel to the WG field without a current bias and formed between the ppL 1 and the ppL 2 .
3 . The device of claim 1 , wherein the ppL 2 comprises a non-magnetic material.
4 . The device of claim 1 , wherein the pxL is an alloy or multilayer made of one or more of Cr, Ir, NiCr, Ta, W, Pt, Pd, Rh, Ti and Ru such that a net spin polarization in electrons transiting the pxL is effectively lost.
5 . The device of claim 1 , wherein the ppL 1 , the ppL 2 , and the ppL 3 are one or more of Cu, Au, Ag, Ru, Al, Cr, V, or alloys thereof, and have sufficient spin diffusion length to allow spin polarization in essentially an unaltered orientation for electrons traversing through the ppL 1 , the ppL 2 , and the ppL 3 .
6 . The device of claim 1 , wherein at least one of the nSIL 1 , the nSIL 2 , and the nFGL is a negative spin polarization material with a spin polarization from −0.4 to 0, and is made of an alloy that is of one or more of Fe, Co, and Ni with Cr, V, and Mn, or a multilayer thereof.
7 . The device of claim 1 , wherein the pSP layer has a magnetization ferromagnetically coupled to the MP, and substantially aligned in the WG field direction with or without an application of a direct current (DC) voltage across the STO device.
8 . The device of claim 1 , wherein each of the pSP layer, the nFGL, the nSIL 1 , and the nSIL 2 has a saturation magnetization (Ms) from 6 kiloGauss (KG) to 15 KG, and a thickness from 1 to 4 nm.
9 . The device of claim 1 , wherein the device is part of a head gimbal assembly with a suspension that elastically supports the device, wherein the suspension has a flexure to which the device is joined, a load beam with one end connected to the flexure, and a base plate connected to another end of the load beam.
10 . The device of claim 1 , wherein the device is part of a magnetic recording apparatus with a magnetic recording medium positioned opposite to a slider on which the device is formed.