IP Library › Granted Patent US 8,743,496

Granted Patent B2

US 8,743,496 · App. 13/176,956 · Granted Jun 3, 2014

Servo pattern compatible with planarization constraints of patterned media and use of a single master template

Inventors: Keiichiro Nonaka (Fujisawa, JP); Kei Yasuna (Fujisawa, JP); Masahito Kobayashi (Ushiku, JP)

Assignee: HGST Netherlands B.V.

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Quick Facts

Patent No.: US 8,743,496
App. No.: 13/176,956
Granted: Jun 3, 2014
Kind: B2

External Links

USPTO Patent Center↗ Full Patent PDF↗

Abstract

Embodiments described herein provide for robust servo patterns that comply with planarization constraints and also allow use of a single master template for manufacture of both the front and back of a magnetic disk. Planarization constraints are met because only a portion of servo data is hard patterned on the magnetic disk and the hard patterned servo data areas comply with planarization constraints. The servo pattern has two symmetrical servo write assist patterns, one on each side of a central burst pattern. The servo sync, SAM, track-ID, sector-ID, and/or RRO values can be written magnetically by the write head onto these servo write assist patterns after the completion of the planarization process. The symmetric design of the servo pattern allows both a left-to-right and a right-to-left servo write and read back, thereby enabling use of a single master template in magnetic disk manufacture.

Claims (45)

1. A magnetic disk, comprising:

a plurality of servo patterns, each servo pattern comprising a first servo write assist pattern, a central burst pattern bordering the first servo write assist pattern, and a second servo write assist pattern bordering the central burst pattern,

wherein the first and second servo write assist patterns are substantially symmetrical to each other about the central burst pattern, and

wherein each servo pattern comprises a magnetically written servo sync with at least four magnetic transitions.

2. The magnetic disk of claim 1 , wherein the servo sync of each servo pattern is magnetically written with alternating polarity.

3. The magnetic disk of claim 1 , wherein the servo sync of each servo pattern is magnetically written with uniform polarity.

4. The magnetic disk of claim 1 ,

wherein a plurality of sector address marks (SAMs) are magnetically written into the servo patterns, and

wherein all the SAMs are substantially identical.

5. The magnetic disk of claim 1 , wherein the servo patterns are arranged into servo sectors.

6. The magnetic disk of claim 5 , wherein the servo sectors extend generally straight from an inner diameter of the magnetic disk to an outer diameter of the magnetic disk.

7. The magnetic disk of claim 5 , wherein the servo sectors extend generally arcuately from an inner diameter of the magnetic disk to an outer diameter of the magnetic disk.

8. The magnetic disk of claim 5 ,

wherein each servo pattern comprises a plurality of magnetically written sector-IDs, and

wherein the sector-IDs within each servo sector are substantially identical within that servo sector.

9. The magnetic disk of claim 5 , wherein a plurality of magnetically written start-of-track marks are written within one servo sector.

10. The magnetic disk of claim 1 , wherein at least a portion of a track-ID is magnetically written in each first servo write assist pattern.

11. The magnetic disk of claim 1 , wherein at least a portion of a track-ID is magnetically written in each second servo write assist pattern.

12. The magnetic disk of claim 1 ,

wherein at least a first portion of a track-ID is magnetically written in each first servo write assist pattern; and

wherein at least a second portion of a track-ID is magnetically written in each second servo write assist pattern.

13. The magnetic disk of claim 1 , wherein at least a portion of a sector-ID is magnetically written in each first servo write assist pattern.

14. The magnetic disk of claim 1 , wherein at least a portion of a sector-ID is magnetically written in each second servo write assist pattern.

15. The magnetic disk of claim 1 , wherein the central burst pattern comprises a magnetically written uniform polarity field.

16. The magnetic disk of claim 1 , wherein the central burst pattern comprises a magnetically written alternating polarity field.

17. The magnetic disk of claim 1 , wherein the central burst pattern comprises a magnetically written DC-free null servo burst.

18. The magnetic disk of claim 1 , wherein each of the first and second servo write assist patterns comprises circumferential magnetic rows and circumferential non-magnetic grooves.

19. The magnetic disk of claim 1 , wherein each of the first and second servo write assist patterns comprises at least three radial magnetic columns separated by radial non-magnetic grooves.

20. The magnetic disk of claim 1 , wherein the central burst pattern comprises a plurality of checkerboard sub-patterns.

21. The magnetic disk of claim 1 , wherein the central burst pattern comprises an ABCD pattern.

22. The magnetic disk of claim 1 , wherein the central burst pattern comprises a phase pattern.

23. The magnetic disk of claim 1 , wherein the second servo write assist pattern comprises a magnetically written uniform polarity field.

24. The magnetic disk of claim 1 , wherein the second servo write assist pattern of each servo pattern comprises a plurality of magnetically written repeatable runout values.

25. A method of writing servo data comprising:

(a) patterning both a first and second side of a double-sided magnetic disk with a plurality of substantially identical servo patterns, each servo pattern comprising two servo write assist patterns that are substantially symmetrical to each other about a central burst pattern;

(b) assembling the double-sided magnetic disk into a disk drive system with a first side write head operable for writing on the first side and a second side write head operable for writing on the second side; and

the first encountered of the two servo write assist patterns of each servo pattern on the first side using the first side write head; and

the first encountered of the two servo write assist patterns of each servo pattern on the second side using the second side write head.

26. The method of claim 25 , wherein the servo write assist patterns on the first side are written in a clockwise direction and the servo write assist patterns on the second side are written in a counterclockwise direction.

27. The method of claim 25 , wherein a sector address mark (SAM) is written in the first encountered of the two servo write assist patterns of each servo pattern.

28. The method of claim 25 , wherein at least a portion of a track-ID is written in the first encountered of the two servo write assist patterns of each servo pattern.

29. The method of claim 25 , wherein at least a portion of a track-ID is written in the second encountered of the two servo write assist patterns of each servo pattern.

30. The method of claim 25 , wherein at least a portion of a sector-ID is written in the first encountered of the two servo write assist patterns of each servo pattern.

31. The method of claim 25 , wherein each central burst pattern is magnetically written with DC-free null servo burst.

Assignments (7)

PATENT COLLATERAL AGREEMENT - DDTL LOAN AGREEMENT Recorded Aug 21, 2023

From: WESTERN DIGITAL TECHNOLOGIES, INC.

To: JPMORGAN CHASE BANK, N.A.

Reel/Frame 067045/0156 →

PATENT COLLATERAL AGREEMENT - A&R LOAN AGREEMENT Recorded Aug 21, 2023

From: WESTERN DIGITAL TECHNOLOGIES, INC.

To: JPMORGAN CHASE BANK, N.A.

Reel/Frame 064715/0001 →

RELEASE OF SECURITY INTEREST AT REEL 052915 FRAME 0566 Recorded Feb 8, 2022

From: JPMORGAN CHASE BANK, N.A.