Data storage device detecting NFT contamination by measuring thermal gradient and magnetic write width

Patent metadata

Field	Value
Publication number	US-11430482-B1
Application number	US-202117357030-A
Country	US
Kind code	B1
Filing date	Jun 24, 2021
Priority date	Jun 24, 2021
Publication date	Aug 30, 2022
Grant date	Aug 30, 2022

Abstract

A data storage device is disclosed comprising a head actuated over a magnetic media, wherein the head comprises a write element, a read element, a laser, and a near field transducer. An operating thermal gradient of the magnetic media is periodically measured at an operating power setting for the laser that achieves a target magnetic write width. When a slope of the operating thermal gradient exceeds a threshold, a test thermal gradient and magnetic write width of the magnetic media is measured at multiple power settings for the laser in order to detect a contamination of the near field transducer.

First claim

What is claimed is:

1. A data storage device comprising:
a magnetic media;
a head actuated over the magnetic media, wherein the head comprises a write element, a read element, a laser, and a near field transducer; and
control circuitry configured to:
periodically measure an operating thermal gradient of the magnetic media at an operating power setting for the laser that achieves a target magnetic write width; and
when a slope of the operating thermal gradient exceeds a threshold, measure a test thermal gradient and magnetic write width of the magnetic media at multiple power settings for the laser in order to detect a contamination of the near field transducer.

2. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to detect the contamination of the near field transducer when the test thermal gradient versus the magnetic write width substantially matches a predetermined relationship.

3. The data storage device as recited in claim 2 , wherein the control circuitry is further configured to:
curve fit the test thermal gradient versus magnetic write width to a function; and
compare the curve fitted function to a predetermined function to determine whether the test thermal gradient versus the magnetic write width substantially matches the predetermined relationship.

4. The data storage device as recited in claim 2 , wherein:
the test thermal gradient versus magnetic write width exhibits a first slope when the near field transducer is substantially un-contaminated; and
the test thermal gradient versus magnetic write width exhibits a second slope greater than the first slope when the near field transducer is contaminated.

5. The data storage device as recited in claim 2 , wherein when the slope of the operating thermal gradient exceeds a threshold the control circuitry is further configured to:
measure an offset between the write element and a read element; and
confirm the detected contamination of the near field transducer based on the measured offset between the write element and the read element.

6. A data storage device comprising:
a magnetic media;
a head actuated over the magnetic media, wherein the head comprises a write element, a read element, a laser, and a near field transducer; and
control circuitry configured to measure a test thermal gradient and magnetic write width of the magnetic media at multiple power settings for the laser in order to detect a contamination of the near field transducer.

7. The data storage device as recited in claim 6 , wherein the control circuitry is further configured to:
periodically measure an operating thermal gradient of the magnetic media at an operating power setting for the laser that achieves a target magnetic write width; and
when a slope of the operating thermal gradient exceeds a threshold, measure the test thermal gradient and magnetic write width of the magnetic media at the multiple power settings for the laser in order to detect the contamination of the near field transducer.

8. The data storage device as recited in claim 6 , wherein the control circuitry is further configured to detect the contamination of the near field transducer when the test thermal gradient versus the magnetic write width substantially matches a predetermined relationship.

9. The data storage device as recited in claim 8 , wherein the control circuitry is further configured to:
curve fit the test thermal gradient and magnetic write width measurements to a function; and
compare the curve fitted function to a predetermined function to determine whether the test thermal gradient versus the magnetic write width substantially matches the predetermined relationship.

10. The data storage device as recited in claim 6 , wherein:
the test thermal gradient versus magnetic write width measurements exhibits a first slope when the near field transducer is substantially un-contaminated; and
the test thermal gradient versus magnetic write width measurements exhibits a second slope greater than the first slope when the near field transducer is contaminated.

11. The data storage device as recited in claim 6 , wherein the control circuitry is further configured to:
measure an offset between the write element and a read element; and
confirm the detected contamination of the near field transducer based on the measured offset between the write element and the read element.

12. A data storage device comprising:
a magnetic media;
a head actuated over the magnetic media, wherein the head comprises a write element, a read element, a laser, and a near field transducer; and
control circuitry configured to:
periodically measure an operating thermal gradient of the magnetic media at an operating power setting for the laser that achieves a target magnetic write width; and
when a slope of the operating thermal gradient exceeds a threshold, measure an offset between the write element and the read element in order to detect a contamination of the near field transducer.

13. The data storage device as recited in claim 12 , wherein when the slope of the operating thermal gradient exceeds the threshold the control circuitry is further configured to:
measure a test thermal gradient and magnetic write width of the magnetic media at multiple power settings for the laser; and
confirm the detected contamination of the near field transducer based on the measured test thermal gradient and magnetic write width at the multiple power settings for the laser.

14. The data storage device as recited in claim 13 , wherein the control circuitry is further configured to detect the contamination of the near field transducer when the test thermal gradient versus the magnetic write width substantially matches a predetermined relationship.

15. The data storage device as recited in claim 14 , wherein the control circuitry is further configured to:
curve fit the test thermal gradient versus magnetic write width to a function; and
compare the curve fitted function to a predetermined function to determine whether the test thermal gradient versus the magnetic write width substantially matches the predetermined relationship.

16. The data storage device as recited in claim 13 , wherein:
the test thermal gradient versus magnetic write width exhibits a first slope when the near field transducer is substantially un-contaminated; and
the test thermal gradient versus magnetic write width exhibits a second slope greater than the first slope when the near field transducer is contaminated.

17. A data storage device comprising:
a magnetic media;
a head actuated over the magnetic media, wherein the head comprises a write element, a read element, a laser, and a near field transducer; and
a means for measuring a test thermal gradient and magnetic write width of the magnetic media at multiple power settings for the laser in order to detect a contamination of the near field transducer.

18. The data storage device as recited in claim 17 , further comprising:
a means for periodically measuring an operating thermal gradient of the magnetic media at an operating power setting for the laser that achieves a target magnetic write width; and
when a slope of the operating thermal gradient exceeds a threshold, a means for measuring the test thermal gradient and magnetic write width of the magnetic media at the multiple power settings for the laser in order to detect the contamination of the near field transducer.

19. The data storage device as recited in claim 17 , further comprising a means for det

Assignees

• Western Digital Tech Inc

Inventors

• Rajauria Sukumar
• Smith Robert Lee
• Tahmasebi Taiebeh

Classifications

• G11B2005/0021

  Thermally assisted recording using an auxiliary energy source for heating the recording layer locally to assist the magnetization reversal · CPC title

• G11B11/24 Primary

  using recording by near-field interactions · CPC title

• G11B5/3189

  Testing · CPC title

• G11B21/106 Primary

  on disks · CPC title

• G11B5/012

  Recording on, or reproducing or erasing from, magnetic disks (G11B17/00, G11B19/00 take precedence) · CPC title