Modified field generation layer for microwave assisted magnetic recording

• US 8,208,219 B2
• Filed: 11/05/2010
• Issued: 06/26/2012
• Est. Priority Date: 11/05/2010
• Status: Active Grant

• Current Assignee: Headway Technologies Incorporated (TDK Corporation)
• Original Assignee: Headway Technologies Incorporated (TDK Corporation)
• Inventors: Zhang, Kunliang, Li, Min, Zhou, Yuchen
• Primary Examiner(s): EVANS, JEFFERSON A
• Application Number:
  US12/927,083
• Publication Number:
  US 20120113540A1
• Time in Patent Office: 599 Days
• Field of Search: 360/324.1, 360/324.11, 360/324.12, 360/324.2, 360/125.03, 360/125.3
• US Class Current: 360/125.03
• CPC Class Codes: G11B 2005/001 Controlling recording characteristics of record carriers or transducing characteristics of transducers by means not being part of their structure
• CPC Class Codes: G11B 2005/0024 Microwave assisted recording
• CPC Class Codes: G11B 5/1278 specially adapted for magnetisations perpendicular to the surface of the record carrier
• CPC Class Codes: G11B 5/3133 including layers not usually being a part of the electromagnetic transducer structure and providing additional features, e.g. for improving heat radiation, reduction of power dissipation, adaptations for measurement or indication of gap depth or other properties of the structure G11B5/3106 takes precedence

Abstract

A spin torque oscillator is described in which the conventional Field Generation Layer (FGL) is replaced by a bilayer, one of whose members exhibits perpendicular magnetic anisotropy while the other exhibits conventional in-plane anisotropy. Provided the layer with the perpendicular anisotropy is the one that is closest to the spacer layer, the device is able to generate microwaves at current densities as low as 1×10⁸ A/cm².

Claims

1. A method to enable a spin torque oscillator (STO) to generate microwaves at low current densities, near a perpendicular write pole, comprising:

providing a non-magnetic spacer layer having parallel opposing first and second outer surfaces;

disposing a field generation layer (FGL) to be in contact with said first outer surface, said FGL being a bilayer of first and second FGL sub-layers;

said first FGL sub-layer being in full contact with said first outer surface as well as having an easy axis that is normal to said first outer surface;

said second FGL sub-layer being in full contact with said first FGL sub-layer as well as having an easy axis that is parallel to said second outer surface; and

disposing a spin injection layer (SIL) to be in full contact with said second outer surface as well as being permanently magnetized normal to said first and second outer surfaces, thereby enabling said STO to generate microwave radiation at low current densities.

2. The method recited in claim 1 wherein said low current densities are in a range of from 5×

10⁷ A/cm² to 5×

10⁸ A/cm².

3. The method of claim 2 wherein ferromagnetic resonance occurs in said STO at frequencies in excess of 30 GHz.

4. The method recited in claim 1 wherein said FGL lies between said SIL and said write pole whereby said STO is a top SIL device.

5. The method recited in claim 1 wherein said SIL lies between said FGL and said write pole whereby said STO is a bottom SIL device.

6. A spin torque oscillator (STO) able to generate microwaves at low current densities, near a perpendicular write pole, comprising:

a non-magnetic spacer layer having parallel opposing first and second outer surfaces;

a field generation layer (FGL) disposed to be in contact with said first outer surface, said FGL being a bilayer of first and second FGL sub-layers;

said first FGL sub-layer being in full contact with said first outer surface as well as having an easy axis that is normal to said first outer surface;

said second FGL sub-layer being in full contact with said first FGL sub-layer as well as having an easy axis that is parallel to said second outer surface; and

a spin injection layer (SIL) that is in full contact with said second outer surface as well as being permanently magnetized normal to said first and second outer surfaces, whereby said STO is able to generate microwave radiation at low current densities.

7. The STO described in claim 6 wherein said low current densities are in a range of from 5×

10⁷ A/cm² to 5×

10⁸ A/cm².

8. The STO described in claim 6 wherein ferromagnetic resonance occurs at frequencies in excess of 30 GHz.

9. The STO described in claim 6 wherein said FGL lies between said SIL and said write pole whereby said STO is a top SIL device.

10. The STO described in claim 6 wherein said SIL lies between said FGL and said write pole whereby said STO is a bottom SIL device.

11. The STO described in claim 6 wherein said non-magnetic spacer is selected from the group consisting of Cu, MgO, AlOx, TiOx, ZnO and current confining paths (CCP) such as Cu/CCP(such as AlCu/PIT/IAO etc)/Cu or Cu/ZnO/Cu etc.

12. A bottom spin injection layer (SIL) spin torque oscillator (STO), comprising:

a seed layer of Cu on Ru on Ta;

a first multilayer structure on said seed layer, said first multilayer structure further comprising t1 Å

of Ni on t2 Å

of Co_100-xFe_x, repeated n times;

a non-magnetic spacer layer on said first multilayer structure;

a second multilayer structure on said non-magnetic spacer layer, said second multilayer structure further comprising t3 Å

of Ni on t4 Å

of Co_100-yFe_y, repeated m times;

a layer of FeCo on said second multilayer structure; and

on said layer of FeCo, a capping layer of Ru on Ta on Ru.

13. The bottom SIL STO described in claim 12 wherein, for said seed layer, said Ta layer has a thickness ranging from 5 to 50 Å

, said Ru layer has a thickness ranging from 5 to 100 Å

, and said Cu layer has a thickness ranging from 0 to 100 Å

.

14. The bottom SIL STO described in claim 12 wherein, for said multi-layer structures, said t2 or t4 thickness of each Co_100-xFe_x layer is in a range of from 1.5 to 3 Å

, said t1 or t3 thickness of Ni is in a range of from 3.5 to 8 Å

, and x in said Co_100-xFe_x formulation, is in a range of from 0 to 90%.

15. The bottom SIL STO described in claim 12 wherein, for said multi-layer structures, said t2 or t4 thickness of each Co_100-xFe_x layer is in a range of from 0.5 to 5 Å

, said t1 or t3 thickness of Ni is in a range of from 2 to 10 Å

, and x in said Co_100-xFe_x formulation, is in a range of from 0 to 90%.

16. The bottom SIL STO described in claim 12 wherein n or m, the number of times said Ni on Co_100-xFe_x formulations may be repeated ranges from 10 to 30.

17. The bottom SIL STO described in claim 12 wherein n or m, the number of times said Ni on Co_100-xFe_x formulations may be repeated ranges from 5 to 50.

18. The bottom SIL STO described in claim 12 wherein, Ni in said [Ni on Co_100-xFe_x] formulation may be replaced by a material selected from the group consisting of Pt, Pd, Ir, CoPt, FePt, CoPd, FePd, TbFe, and TbCo.

19. A top spin injection layer (SIL) spin torque oscillator (STO), comprising:

a seed layer of Cu on Ru on Ta;

a layer of FeCo on said seed layer;

a first multilayer structure on said FeCo layer, said first multilayer structure further comprising t1 Å

of Ni on t2 Å

of Co_100-xFe_x, repeated n times;

a non-magnetic spacer layer on said first multilayer structure;

a second multilayer structure on said non-magnetic spacer layer, said second multilayer structure further comprising t3 Å

of Ni on t4 Å

of Co_100-yFe_y, repeated m times; and

a trilayer of Ru on Ta on Ru on said second multilayer structure.