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

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.