Non-contact laser-induced protrusion measurement apparatus and method

Patent metadata

Field	Value
Publication number	US-9940959-B1
Application number	US-201715615399-A
Country	US
Kind code	B1
Filing date	Jun 6, 2017
Priority date	Dec 10, 2015
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

A method and apparatus are directed to providing relative movement between a slider configured for heat-assisted magnetic recording and a magnetic recording medium, and causing protrusion of a portion of an air bearing surface (ABS) of the slider in response to activating at least a laser source while maintaining spacing between the protrusion and the medium. A magnitude of at least a portion of the protrusion is measured while maintaining spacing between the protrusion and the medium.

First claim

What is claimed is:

1. A method, comprising:
providing relative movement between a magnetic recording medium and a slider configured for heat-assisted magnetic recording, the slider comprising an air bearing surface (ABS) and a thermal sensor at or near the ABS;
causing protrusion of a portion of the ABS of the slider in response to activating at least a laser source while maintaining spacing between the protrusion and the medium;
in the absence of laser excitation, determining a first resistance response of the thermal sensor to varying bias at two or more clearances while maintaining spacing between the slider and the medium;
in the presence of laser excitation, determining a second resistance response of the thermal sensor to varying bias power at the two or more clearances while maintaining spacing between the slider and the medium;
extrapolating a resistance response of the thermal sensor with no bias power, R 0 , using one or both of the first resistance response and the second resistance response; and
determining a magnitude of at least a portion of the protrusion using R 0 .

2. The method of claim 1 , further comprising:
determining an R 0 clearance slope using the first resistance response; and
determining the magnitude of at least the portion of the protrusion using the R 0 clearance slope.

3. The method of claim 1 , wherein:
the protruded portion of the ABS comprises a first region and a second region;
the second region is closer to the medium than the first region; and
determining the magnitude of at least the portion of the protrusion comprises determining the magnitude of the first region.

4. The method of claim 1 , wherein:
the protruded portion of the ABS comprises a first region having a first thermal time constant and a second region having a second thermal time constant;
the second region is closer to the medium than the first region; and
determining the magnitude of at least the portion of the protrusion comprises determining the magnitude of the first region.

5. The method of claim 1 , wherein the portion of the ABS comprises a writer and a near-field transducer of the slider.

6. The method of claim 1 , wherein the portion of the ABS comprises a reader of the slider.

7. The method of claim 1 , further comprising determining the magnitude of at least the portion of the protrusion at different diameters or zones of the medium.

8. An apparatus, comprising:
a slider configured for heat-assisted magnetic recording and comprising one or more thermal sensors at or near an air bearing surface (ABS) of the slider, wherein excitation of a laser source causes protrusion of a portion of the ABS extending toward, but spaced apart from, a magnetic recording medium; and
a processor coupled to the one or more thermal sensors and configured to:
in the absence of laser excitation, determine a first resistance response of the thermal sensor to varying bias power at two or more clearances while maintaining spacing between the slider and the medium;
in the presence of laser excitation, determine a second resistance response of the thermal sensor to varying bias power at the two or more clearances while maintaining spacing between the slider and the medium;
extrapolate a resistance response of the thermal sensor with no bias power, R 0 using one or both of the first resistance response and the second resistance response; and
determine a magnitude of at least a portion of the protrusion using R 0 .

9. The apparatus of claim 8 , wherein:
the protruded portion of the ABS comprises a first region and a second region;
the second region is closer to the medium than the first region; and
the processor is configured to determine the magnitude of the first region.

10. The apparatus of claim 8 , wherein:
the protruded portion of the ABS comprises a first region having a first thermal time constant and a second region having a second thermal time constant;
the second region is closer to the medium than the first region; and
the processor is configured to determine the magnitude of the first region.

11. The apparatus of claim 8 , wherein:
one of the thermal sensors is situated at each of a plurality of slider locations subject to ABS protrusion in response to excitation of the laser source; and
the processor is configured to determine the magnitude of at least a portion of each ABS protrusion using the thermal sensor proximate each ABS protrusion.

12. The apparatus of claim 8 , wherein the portion of the ABS comprises a writer and a near-field transducer of the slider.

13. The apparatus of claim 8 , wherein the portion of the ABS comprises a reader of the slider.

14. The apparatus of claim 8 , wherein the processor is configured to determine the magnitude of at least the portion of the protrusion at different diameters or zones of the medium.

15. A method, comprising:
providing relative movement between a magnetic recording medium and a slider configured for heat-assisted magnetic recording, the slider comprising an air bearing surface (ABS) and a thermal sensor at or near the ABS;
causing protrusion of a portion of the ABS of the slider in response to activating at least a laser source while maintaining spacing between the protrusion and the medium;
calculating a resistance response, R 0 , as a resistance of the thermal sensor with no bias power supplied to the thermal sensor;
in the absence of laser excitation, determining a first resistance response of the thermal sensor to varying clearance while maintaining spacing between the slider and the medium;
calculating a first value indicative of R 0 dependence on clearance based on the first resistance response;
in the presence of laser excitation, determining a second resistance response of the thermal sensor to varying clearance while maintaining spacing between the slider and the medium, wherein the laser excitation causes protrusion of a portion of the ABS;
calculating a second value indicative of R 0 dependence on clearance based on the second resistance response; and
determining a magnitude of at least a portion of the protrusion using the first value and the second value.

16. The method of claim 15 , wherein:
the protruded portion of the ABS comprises a first region and a second region;
the second region is closer to the medium than the first region; and
determining the magnitude of at least the portion of the protrusion comprises determining the magnitude of the first region.

17. The method of claim 15 , wherein:
the protruded portion of the ABS comprises a first region having a first thermal time constant and a second region having a second thermal time constant;
the second region is closer to the medium than the first region; and
determining the magnitude of at least the portion of the protrusion comprises determining the magnitude of the first region.

18. The method of claim 15 , wherein the portion of the ABS comprises a writer and a near-field transducer of the slider.

19. The method of claim 15 , wherein the portion of the ABS comprises a reader of the slider.

20. The method of claim 15 , further comprising determining the magnitude of at least the portion of the protrusion at different diameters or zones of the medium.

Assignees

• Seagate Technology Llc

Inventors

• Granz Steven Douglas
• Johnson Michael Thomas

Classifications

• G11B11/10506

  by modulating only the light beam of the transducer · CPC title

• G11B2005/0021

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

• G11B5/6082

  Design of the air bearing surface · CPC title

• G11B5/6052 Primary

  using optical means · CPC title

• G11B7/126

  Circuits, methods or arrangements for laser control or stabilisation · CPC title