APPARATUS AND METHOD FOR WRITING TO MAGNETIC MEDIA USING AN AC BIAS CURRENT TO ENHANCE THE WRITE FIELD

• US 20190325902A1
• Filed: 07/01/2019
• Published: 10/24/2019
• Est. Priority Date: 12/30/2016
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: DE ALBUQUERQUE, Goncalo Marcos Baiao, DING, Yunfei, GONCHAROV, Alexander, HO, Kuok San, MAURI, Daniele, MIHAJLOVIC, Goran, SONG, Suping, VAN DER HEIJDEN, Petrus Antonius
• Granted Patent: US 10,643,642 B2
• Time in Patent Office: Days
• 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 5/09 Digital recording
• CPC Class Codes: G11B 5/314 where the layers are extra layers normally not provided in the transducing structure, e.g. optical layers G11B5/3196 takes precedence
• CPC Class Codes: G11B 5/3146 magnetic layers

Abstract

An apparatus comprises a main pole, a trailing shield, a write-field-enhancing structure, a write coil, a write current control circuit configured to supply a write current to the write coil to record a bit to a magnetic medium, and a driving current control circuit configured to supply a driving current to the write-field-enhancing structure, wherein the driving current comprises a driving pulse, and wherein the driving current comprises an AC component with a duty cycle selected based at least in part on a power constraint. A method of writing to a magnetic medium comprises supplying a write current to a write coil of a magnetic write head, and supplying a driving current to a free layer disposed in a write gap between a main pole and a trailing shield, wherein the driving current comprises an AC component with a duty cycle based at least in part on a power constraint.

Claims

1. An apparatus for writing to a magnetic medium, the apparatus comprising:

a main pole;

a trailing shield;

a write-field-enhancing structure disposed within a write gap between the main pole and the trailing shield, the write-field-enhancing structure comprising;

a spacer disposed between the main pole and the trailing shield, wherein the spacer is non-magnetic,

a non-magnetic layer disposed between the main pole and the trailing shield, and

a free layer adjacent to the spacer and disposed between the spacer and the non-magnetic layer, wherein the free layer is magnetic;

a write coil configured to magnetize the main pole;

a write current control circuit configured to supply a write current to the write coil to record a bit to a magnetic medium, wherein the write current comprises a write pulse; and

a driving current control circuit configured to supply a driving current to the write-field-enhancing structure, wherein the driving current comprises a driving pulse, and wherein the driving current comprises an AC component with a duty cycle selected based at least in part on a power constraint.

2. The apparatus recited in claim 1, wherein the driving pulse is delayed by an amount of time relative to the write pulse.

3. The apparatus recited in claim 2, wherein the amount of time is less than approximately 500 picoseconds.

4. The apparatus recited in claim 1, wherein a timing of the driving pulse is based on a timing of the write pulse.

5. The apparatus recited in claim 1, wherein a duration of the driving pulse is greater than zero and less than approximately 500 picoseconds.

6. The apparatus recited in claim 1, wherein the driving pulse has at least two non-zero amplitudes.

7. The apparatus recited in claim 1, wherein the driving current control circuit is further configured to adjust at least one characteristic of the driving pulse based on the write current or based on an upcoming bit to be recorded.

8. The apparatus recited in claim 7, wherein the at least one characteristic of the driving pulse comprises an amplitude, a delay relative to the write pulse, or a duration.

9. The apparatus recited in claim 1, wherein the driving current further comprises an advance pulse preceding the driving pulse.

10. The apparatus recited in claim 9, wherein an amplitude of the advance pulse is less than an amplitude of the driving pulse, or less than or equal to zero.

11. The apparatus recited in claim 9, wherein the driving current control circuit is further configured to adjust at least one characteristic of the advance pulse based on the write current or based on an upcoming bit to be recorded.

12. The apparatus recited in claim 11, wherein the at least one characteristic of the advance pulse comprises an amplitude, a delay relative to the write pulse, or a duration.

13. The apparatus recited in claim 1, wherein the free layer is the only magnetic layer within the write gap that is not adjacent to the main pole or the trailing shield.

14. A data storage device, comprising:

the apparatus recited in claim 1; and

the magnetic medium.

15. A method of writing to a magnetic medium, the method comprising:

supplying a write current to a write coil of a magnetic write head;

supplying a driving current to a free layer disposed in a write gap between a main pole and a trailing shield of the magnetic write head, wherein the driving current comprises an AC component; and

selecting a duty cycle of the AC component based at least in part on a power constraint.

16. The method recited in claim 15, further comprising:

determining a timing of the AC component based on an upcoming bit to be recorded on the magnetic medium,

and wherein supplying the driving current to the free layer is based on the upcoming bit.

17. The method recited in claim 15, further comprising:

selecting a timing of the driving current relative to the write current.

18. The method recited in claim 15, further comprising:

selecting a duration or amplitude of the AC component based at least in part on the power constraint.

19. The method recited in claim 15, wherein the AC component comprises an advance pulse and a driving pulse, wherein the advance pulse precedes the driving pulse.

20. The method recited in claim 19, wherein an amplitude of the advance pulse is less than an amplitude of the driving pulse, or less than or equal to zero.

21. The method recited in claim 15, further comprising:

optimizing at least one characteristic of the AC component based on the write current, wherein the at least one characteristic comprises an amplitude, a delay relative to a write pulse of the write current, the duty cycle, or a duration.

22. The method recited in claim 15, wherein the free layer is the only magnetic layer within the write gap that is not adjacent to the main pole or the trailing shield of the magnetic write head.

23. An apparatus for writing to a magnetic medium, the apparatus comprising:

means for supplying a write current to a write coil of a magnetic write head; and

means for supplying a driving current to a free layer disposed in a write gap between a main pole and a trailing shield of the magnetic write head, wherein the driving current comprises an AC component with a duty cycle selected based at least in part on a power constraint.