Implementing spin torque oscillator power-on oscillation checker for microwave-assisted magnetic recording hard disk drives

• US 9,001,444 B1
• Filed: 06/26/2014
• Issued: 04/07/2015
• Est. Priority Date: 06/26/2014
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: HGST Netherlands B.V. (Western Digital Corporation)
• Inventors: Contreras, John, Garzon, Samir Y., Zakai, Rehan Ahmed
• Primary Examiner(s): TRAN, THANG V
• Application Number:
  US14/316,732
• Time in Patent Office: 285 Days
• Field of Search: None
• US Class Current: 360/31
• CPC Class Codes: G11B 2005/0024 Microwave assisted recording
• CPC Class Codes: G11B 5/012 Recording on, or reproducing or erasing from, magnetic disks G11B17/00, G11B19/00 take precedence
• CPC Class Codes: G11B 5/127 Structure or manufacture of heads, e.g. inductive
• CPC Class Codes: G11B 5/40 Protective measures on heads, e.g. against excessive temperature G11B5/31 takes precedence; protection against wear G11B5/255 ; protective structure of the head: see under structures, e.g. G11B5/3106
• CPC Class Codes: G11B 5/455 Arrangements for functional testing of heads; Measuring arrangements for heads

Abstract

A method, apparatus, and system are provided for implementing a power-on spin-torque oscillator (STO) oscillation checker to monitor STO resistance to identify STO oscillation with microwave assisted magnetic recording (MAMR) hard disk drives (HDDs). An amplitude modulated write coil drive current is applied to the write coil in the presence of a DC bias current applied to the STO. The amplitude modulated write coil drive current modulates the STO resistance monitored using an amplifier circuit to identify STO oscillation, used to ensure stable MAMR HDD write operation.

Claims

1. A method for implementing a spin-torque oscillator (STO) oscillation checker for microwave assisted magnetic recording (MAMR) hard disk drives (HDDs) comprising:

applying an amplitude modulated write coil current to a write coil coupled to a spin-torque oscillator (STO) at power-on and periodically during MAMR HDD operation;

using an amplifier circuit coupled to the STO, monitoring STO voltage responsive to the applied amplitude modulated write coil current to identify STO resistance modulation;

using said identified STO resistance modulation to identify STO oscillation; and

using the identified STO oscillation to ensure stable MAMR HDD write operation.

2. The method as recited in claim 1 wherein applying an amplitude modulated write coil current to the write coil coupled to the spin-torque oscillator (STO) includes applying a pulsed constant frequency write coil current to the write coil coupled to the spin-torque oscillator (STO).

3. The method as recited in claim 1 wherein applying an amplitude modulated write coil current to the write coil coupled to the spin-torque oscillator (STO) includes applying a pulsed fixed amplitude alternating frequency write coil current to the write coil coupled to the spin-torque oscillator (STO).

4. The method as recited in claim 1 includes applying a constant direct current (DC) bias current to the spin-torque oscillator (STO).

5. The method as recited in claim 1 wherein using the amplifier circuit coupled to the STO, monitoring STO voltage responsive to the applied amplitude modulated write coil current to identify STO resistance modulation includes providing a threshold detector coupled to an output of the amplifier circuit.

6. An apparatus for implementing a spin-torque oscillator (STO) oscillation checker for microwave assisted magnetic recording (MAMR) hard disk drive (HDDs), comprising:

a controller;

at least one disk;

said disk including a disk media for storing data;

a spin-torque oscillator (STO) for microwave assisted magnetic recording (MAMR);

a write coil coupled to said spin-torque oscillator (STO);

the spin-torque oscillator (STO) oscillation checker comprising

a current source applying an amplitude modulated write coil current to the write coil coupled to a spin-torque oscillator (STO) at power-on and periodically during MAMR HDD operation;

an amplifier circuit coupled to the STO, monitoring STO voltage responsive to the applied amplitude modulated write coil current to identify STO resistance modulation, and using said identified STO resistance modulation to identify STO oscillation; and

said controller using the identified STO oscillation to ensure stable MAMR HDD write operation.

7. The apparatus as recited in claim 6 includes control code stored on a non-transitory computer readable medium, and wherein said controller uses said control code to identify STO oscillation, used to ensure stable MAMR HDD write operation.

8. The apparatus as recited in claim 6 includes a Read/Write integrated circuit (IC) coupled to a slider, said slider containing said spin-torque oscillator (STO);

and said spin-torque oscillator (STO) oscillation checker provided in said Read/Write integrated circuit (IC).

9. The apparatus as recited in claim 6 wherein said current source applying an amplitude modulated write coil current to the write coil coupled to the spin-torque oscillator (STO) selectively applies a pulsed constant frequency write coil current to the write coil coupled to the spin-torque oscillator (STO).

10. The apparatus as recited in claim 6 wherein said current source applying an amplitude modulated write coil current to the write coil coupled to the spin-torque oscillator (STO)) selectively applies a pulsed fixed amplitude alternating frequency write coil current to the write coil coupled to the spin-torque oscillator (STO).

11. The apparatus as recited in claim 6 includes a STO bias current source applying a constant DC STO bias current to the spin-torque oscillator (STO).

12. The apparatus as recited in claim 6 includes a threshold detector coupled to an output of the amplifier circuit, said threshold detector used to identify STO resistance modulation including a sudden STO resistance step.

13. A system for implementing a spin-torque oscillator (STO) oscillation checker comprising:

a microwave assisted magnetic recording (MAMR) hard disk drive (HDD), said MAMR HDD comprising a controller;

at least one disk;

said disk including a disk media for storing data;

a spin-torque oscillator (STO) for microwave assisted magnetic recording (MAMR);

a write coil coupled to said spin-torque oscillator (STO);

a Read/Write integrated circuit (IC) coupled to a slider, said slider containing said spin-torque oscillator (STO); and

said Read/Write integrated circuit (IC) implementing the spin-torque oscillator (STO) oscillation checker;

the spin-torque oscillator (STO) oscillation checker comprising

a current source applying an amplitude modulated write coil current to the write coil coupled to a spin-torque oscillator (STO);

an amplifier circuit coupled to the STO, monitoring STO voltage responsive to the applied amplitude modulated write coil current to identify STO resistance modulation, and using said identified STO resistance modulation to identify STO oscillation; and

said controller using the identified STO oscillation to ensure stable MAMR HDD write operation.

14. The system as recited in claim 13 includes control code stored on a non-transitory computer readable medium, and wherein said controller uses said control code to identify STO oscillation during MAMR HDD operation.

15. The system as recited in claim 13 includes a STO bias current source applying a constant DC STO bias current to the spin-torque oscillator (STO).

16. The system as recited in claim 13 wherein said current source applying an amplitude modulated write coil current to the write coil coupled to the spin-torque oscillator (STO) applies a constant frequency write coil current to the write coil coupled to the spin-torque oscillator (STO) at power-on and periodically during MAMR HDD operation.

17. The system as recited in claim 13 wherein said current source applying an amplitude modulated write coil to the write coil coupled to the spin-torque oscillator (STO) selectively applies a pulsed fixed amplitude alternating frequency write coil current to the write coil coupled to the spin-torque oscillator (STO) at power-on and periodically during MAMR HDD operation.