MgO based perpendicular spin polarizer in microwave assisted magnetic recording (MAMR) applications

Patent metadata

Field	Value
Publication number	US-9966091-B2
Application number	US-201614987127-A
Country	US
Kind code	B2
Filing date	Jan 4, 2016
Priority date	Aug 26, 2014
Publication date	May 8, 2018
Grant date	May 8, 2018

Abstract

A design for a microwave assisted magnetic recording device is disclosed wherein a spin torque oscillator (STO) between a main pole and write shield has a spin polarization (SP) layer less than 30 Angstroms thick and perpendicular magnetic anisotropy (PMA) induced by an interface with one or two metal oxide layers. Back scattered spin polarized current from an oscillation layer is used to stabilize SP layer magnetization. One or both of the metal oxide layers may be replaced by a confining current pathway (CCP) structure. In one embodiment, the SP layer is omitted and spin polarized current is generated by a main pole/metal oxide interface. A direct current or pulsed current bias is applied across the STO. Rf current may also be injected into the STO to reduce critical current density. A write gap of 25 nm or less is achieved while maintaining good STO performance.

First claim

We claim:

1. A microwave assisted magnetic recording (MAMR) structure that includes a write head, comprising:
(a) a main pole that generates a magnetic flux field which is directed through a pole tip at an air bearing surface (ABS) and into a magnetic medium to write one or more bits, the magnetic flux field has a gap field component that is directed across a spin torque oscillator (STO) and into a write shield;
(b) the write shield with a side at the ABS that collects magnetic flux which has passed through the magnetic medium and written the one or more bits;
(c) an external current source that produces a current consisting of a pulsed current in an electrical connection between the main pole and write shield, and across the STO; and
(d) the STO that is formed along the ABS and generates a rf field on the magnetic medium and thereby assists the writing to one or more bits, the STO comprises;
(1) a spin polarization (SP) layer which is a single layer of CoFeB, FeB, or CoB with perpendicular magnetic anisotropy (PMA) that spin polarizes the pulsed current in a direction perpendicular to a top surface of the SP layer and towards an oscillation layer (OL);
(2) the oscillation layer (OL) wherein the spin polarized current of a critical current density from the SP layer causes magnetization in the OL to oscillate with a sufficiently large angle and frequency to generate the rf field on the magnetic medium to assist the writing to one or more bits;
(3) a non-magnetic spacer between the SP layer and OL;
(4) a seed layer formed between the main pole and the OL; and
(5) a capping layer formed between the SP layer and the write shield wherein at least one of the capping layer and the non-magnetic spacer comprises a metal oxide layer that induces the PMA in the SP layer.

2. The MAMR structure of claim 1 wherein the SP layer is comprised of CoFeB, CoFe, a Co alloy, or a Fe alloy with a thickness less than 30 Angstroms.

3. The MAMR structure of claim 1 wherein the PMA in the SP layer may be increased by decreasing a SP layer thickness and by employing a metal oxide layer in both of the capping layer and non-magnetic spacer.

4. The MAMR structure of claim 1 wherein back scattered spin polarized current from the OL works with a damping torque to stabilize the SP layer against undesired magnetization switching in the SP layer.

5. The MAMR structure of claim 1 wherein a thickness of the STO in a down-track direction between the main pole and write shield represents a write gap (WG) distance, and the WG distance is about 25 nm or less.

6. The MAMR structure of claim 1 wherein the capping layer is a metal oxide layer or laminate that is comprised of one or more of MgO, AlOx, TaOx, and RuOx.

7. The MAMR structure of claim 1 wherein the non-magnetic spacer is a metal oxide layer or laminate that is comprised of one or more of AlOx, MgO, AlTiOx, MgZnOx, and ZnOx.

8. The MAMR structure of claim 1 wherein both of the capping layer and non-magnetic spacer are metal oxide layers, the capping layer is comprised of one or more of MgO, AlOx, TaOx, and RuOx, and the non-magnetic spacer is comprised of one or more of AlOx, MgO, AlTiOx, MgZnOx, and ZnOx.

9. The MAMR structure of claim 1 wherein the OL is comprised of a Co alloy, a Fe alloy, or is a laminate with an (A1/A2) n stack of layers where n is a lamination number, A1 is one of Co, Fe, CoFe, CoFeR in which R is a non-magnetic element, and A2 is one of Ni, NiCo, and NiFe.

10. The MAMR structure of claim 1 wherein a rf current that is provided by a rf current generator is combined with the pulsed current through a bias T in the electrical connection across the STO to reduce the critical current density.

11. A microwave assisted magnetic recording (MAMR) structure that includes a write head, comprising:
(a) a main pole that generates a magnetic flux field which is directed through a pole tip at an air bearing surface (ABS) and into a magnetic medium to write one or more bits, the magnetic flux field has a gap field component that is directed across a spin torque oscillator (STO) and into a write shield;
(b) the write shield with a side at the ABS that collects magnetic flux which has passed through the magnetic medium and written the one or more bits;
(c) an external current source that produces a direct current or pulsed current between the main pole and write shield, and across the STO; and
(d) the STO that is formed along the ABS and generates a rf field on the magnetic medium and thereby assists the writing to one or more bits, the STO comprises;
(1) a spin polarization (SP) layer with perpendicular magnetic anisotropy (PMA) that spin polarizes the direct current or pulsed current in a direction perpendicular to a top surface of the SP layer and towards an oscillation layer (OL);
(2) the oscillation layer (OL) wherein the spin polarized current of a critical current density from the SP layer causes magnetization in the OL to oscillate with a sufficiently large angle and frequency to generate the rf field on the magnetic medium to assist the writing to one or more bits;
(3) a non-magnetic spacer that is made of a metal oxide between the SP layer and OL;
(4) a seed layer formed between the main pole and the OL; and
(5) a capping layer that consists of RuOx, or RuOx with TaOx or AlOx and formed between the SP layer and the write shield wherein the non-magnetic spacer and capping layer induce the PMA in the SP layer.

Assignees

• Headway Tech Inc

Inventors

• Chen Wenyu
• Wu Yan

Classifications

• G11B5/314 Primary

  where the layers are extra layers normally not provided in the transducing structure, e.g. optical layers (G11B5/3196 takes precedence) · CPC title

• G11B5/3909

  Arrangements using a magnetic tunnel junction · CPC title

• G11B5/3146

  magnetic layers · CPC title

• G11B5/315 Primary

  Shield layers on both sides of the main pole, e.g. in perpendicular magnetic heads · CPC title

• G11B5/147

  with cores being composed of metal sheets, i.e. laminated cores {with cores composed of isolated magnetic layers, e.g. sheets (in thin films G11B5/31)} · CPC title