Implementing integrated spin-torque oscillator and interface bias control for hard disk drives

• US 8,570,684 B1
• Filed: 10/05/2012
• Issued: 10/29/2013
• Est. Priority Date: 10/05/2012
• Status: Active Grant

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: HGST Netherlands B.V. (Western Digital Corporation)
• Inventors: Contreras, John Thomas, Tagawa, Ikuya, Wallash, Albert John
• Primary Examiner(s): HUBER, PAUL W
• Application Number:
  US13/646,614
• Time in Patent Office: 389 Days
• Field of Search: None
• US Class Current: 360/110
• CPC Class Codes: G11B 2005/0024 Microwave assisted recording
• CPC Class Codes: G11B 5/02 Recording, reproducing, or erasing methods; Read, write or erase circuits therefor

Abstract

A method, apparatus, and system for implementing spin integrated spin-torque oscillator (STO) with an interface bias control for hard disk drives. Bias circuitry for a spin-torque oscillator (STO) is integrated with a slider for microwave assisted magnetic recording (MAMR). The slider includes read and write transducers and the integrated STO bias circuitry controls a bias potential applied to a write return pole to the write transducer with respect to a disk.

Claims

1. A method for implementing an integrated spin-torque oscillator (STO) with an interface bias control for hard disk drives comprising:

providing integrated bias circuitry for the spin-torque oscillator (STO) coupled a slider for microwave assisted magnetic recording (MAMR);

providing a read transducer and a write transducer with the slider;

said write transducer including a write pole and a write return pole; and

controlling a bias potential applied to said write return pole with respect to a disk media with said integrated STO bias circuitry.

2. The method as recited in claim 1 includes providing a spin-torque oscillator (STO) element coupled between said write pole and said write return pole.

3. The method as recited in claim 1 wherein providing integrated bias circuitry for the spin-torque oscillator (STO) coupled a slider for microwave assisted magnetic recording (MAMR includes implementing said integrated STO bias circuitry in a Read/Write integrated circuit (IC).

4. The method as recited in claim 1 wherein providing integrated bias circuitry for the spin-torque oscillator (STO) coupled a slider for microwave assisted magnetic recording (MAMR) includes implementing said integrated STO bias circuitry with at least one slider connection to an ISB bias line.

5. The method as recited in claim 1 wherein providing integrated bias circuitry for the spin-torque oscillator (STO) coupled a slider for microwave assisted magnetic recording (MAMR) includes providing a slider connection with high-frequency low-impedance path to the system ground.

6. The method as recited in claim 1 wherein providing integrated bias circuitry for the spin-torque oscillator (STO) coupled a slider for microwave assisted magnetic recording (MAMR) includes providing at least one slider connection with a transducer connection to a common potential connecting to an ISB bias line and voltage potential.

7. The method as recited in claim 1 wherein controlling said bias potential applied to said write return pole with respect to said disk with said integrated STO bias circuitry includes providing a controllable bias potential with respect to media of less than one Volt, to prevent head-to-disk breakdown electrostatic discharge (ESD) damage.

8. The method as recited in claim 1 wherein controlling said bias potential applied to said write return pole with respect to said disk with said integrated STO bias circuitry includes providing current limit protection for conductive asperities to the disk.

9. The method as recited in claim 1 wherein controlling said bias potential applied to said write return pole with respect to said disk with said integrated STO bias circuitry includes providing a voltage offset resistor bias to said write pole.

10. The method as recited in claim 1 wherein controlling said bias potential applied to said write return pole with respect to said disk with said integrated STO bias circuitry includes providing an independent STO bias potential coupled by an independent STO pad connected to said write pole.

11. An apparatus for implementing an integrated spin-torque oscillator (STO) with an interface bias control for hard disk drives comprising:

a slider including a read transducer and a write transducer;

said write transducer including a write pole and a write return pole;

the spin-torque oscillator (STO) integrated with said slider for microwave assisted magnetic recording (MAMR);

STO bias circuitry coupled to said slider and controlling a bias potential applied to said write return pole with respect to a disk media with said integrated STO bias circuitry.

12. The apparatus as recited in claim 11 includes a spin-torque oscillator (STO) element coupled between said write pole and said write return pole.

13. The apparatus as recited in claim 11 includes a Read/Write integrated circuit (IC) implementing said integrated STO bias circuitry.

14. The apparatus as recited in claim 11 wherein said integrated STO bias circuitry includes at least one slider connection to an ISB bias line.

15. The apparatus as recited in claim 11 wherein said integrated STO bias circuitry includes a slider connection with high-frequency low-impedance path to the system ground.

16. The apparatus as recited in claim 11 wherein said integrated STO bias circuitry includes a pair of transconductance amplifiers with current biases and feedback for providing adjustability of loop gain, and characteristic changes for output impedance and bandwidth.

17. The apparatus as recited in claim 16 wherein said integrated STO bias circuitry includes an overall Laplace transfer function represented by

Vsbd/Vin=(gm₁R₁gm₂R₂)/(R₁C₁s+gm₁R₁gm₂R₂)

where gm₁ and gm₂ represent gain of said transconductance amplifiers, and R₁ C₁ s and R₂ represent biasing and feedback resistors and capacitance.

18. The apparatus as recited in claim 11 includes a voltage offset resistor bias coupled between said write pole and a system ground potential.

19. The apparatus as recited in claim 11 includes an independent STO bias potential coupled by an independent STO pad connected to said write pole.

20. A system for implementing an integrated spin-torque oscillator (STO) with an interface bias control for hard disk drives comprising:

at least one disk;

said disk including a disk media for storing data;

a slider including a read transducer and a write transducer;

said write transducer including a write pole and a write return pole;

the spin-torque oscillator (STO) integrated with said slider for microwave assisted magnetic recording (MAMR);

STO bias circuitry coupled to said slider and controlling a bias potential applied to said write return pole with respect to a disk media with said integrated STO bias circuitry.

21. The system as recited in claim 20 includes a spin-torque oscillator (STO) element coupled between said write pole and said write return pole.

22. The system as recited in claim 20 includes a Read/Write integrated circuit (IC) implementing said integrated STO bias circuitry.