In-situ smear detection and mitigation in heat-assisted magnetic recording head-disk interface

1. A method for detecting contamination at a head-disk interface (HDI) in a heat-assisted magnetic recording (HAMR) hard disk drive (HDD), the method comprising:

flying a head slider over a magnetic-recording disk at a particular fly height;

applying an oscillating signal to a heat source associated with a HAMR near-field transducer (NFT) that is constituent to said head slider to dither the spacing between said NFT and said disk; and

determining, based on a change to a contact detection signal, that contamination has accumulated on said head slider.

2. The method of claim 1 , further comprising:

burnishing said contamination from said head slider.

3. The method of claim 2 , wherein said burnishing includes applying a voltage between said head slider and said disk to bring said head slider into contact with said disk.

4. The method of claim 2 , wherein said burnishing includes applying a particular power signal to a thermal fly height control (TFC) heater element to bring said head slider into contact with said disk.

5. The method of claim 1 , wherein said determining includes determining that said contamination has accumulated on said NFT.

6. The method of claim 1 , wherein said contact detection signal corresponds to a real-time TFC power with said oscillating signal applied, and wherein said determining includes comparing said contact detection signal with a known TFC power corresponding to an NFT touchdown without contamination accumulation.

7. The method of claim 6 , further comprising:

computing an extent of said contamination based on a difference between said contact detection signal and said known TFC power.

8. The method of claim 1 , wherein said contamination is generated, at least in part, based on heat generated by said heat source during operation.

9. The method of claim 1 , wherein a part of said NET that changes shape in response to applying said oscillating signal to said heat source is dimensioned on the order of a few hundred nanometers by a few hundred nanometers, and thereby said determining has a precision on the same order of a few hundred nanometers by a few hundred nanometers.

10. The method of claim 1 , wherein said applying includes applying said oscillating signal at a natural frequency of said head slider.

11. A hard disk drive (HDD) comprising:

a disk medium rotatably mounted on a spindle;

a head slider comprising a read-write head configured to read from and to write to said disk medium;

a voice coil actuator configured to move said head slider to access portions of said disk medium; and

a least one electronic component comprising a memory, one or more processors, and one or more sequences of instructions which, when executed by said one or more processors, cause performance of:

flying a head slider over said disk medium at a particular fly height,

applying an oscillating signal to a heat source associated with a heat-assisted magnetic recording (HAMR) near-field transducer (NFT) that is constituent to said head slider to dither the spacing between said NET and said medium disk, and

determining, based on a change to a contact detection signal, that contamination has accumulated on said head slider.

12. The hard disk drive of claim 11 , wherein said one or more sequences of instructions, when executed, further cause performance of:

burnishing said contamination from said head slider.

13. The hard disk drive of claim 12 , wherein said burnishing includes applying a voltage between said head slider and said disk medium to bring said head slider into contact with said disk medium.

14. The hard disk drive of claim 12 , wherein said burnishing includes applying a particular power signal to a thermal fly height control (TFC) heater element to bring said head slider into contact with said disk medium.

15. The hard disk drive of claim 11 , wherein said determining includes determining that said contamination has accumulated on said NFT.

16. The hard disk drive of claim 11 , wherein said contact detection signal corresponds to a real-time TFC power with said oscillating signal applied, and wherein said determining includes comparing said contact detection signal with a known TFC power corresponding to an NFT touchdown without contamination accumulation.

17. The hard disk drive of claim 16 , wherein said one or more sequences of instructions, when executed, further cause performance of:

computing an extent of said contamination based on a difference between said contact detection signal and said known TFC power.

18. An electronic component comprising:

a memory;

one or more processors; and

one or more sequences of instructions in said memory and which, when executed by said one or more processors, cause performance of:

flying a head slider over a magnetic-recording disk at a particular fly height,

applying an oscillating signal to a heat source associated with a heat-assisted magnetic recording (HAMR) near-field transducer (NFT) that is constituent to said head slider to dither the spacing between said NET and said disk, and

determining, based on a change to a contact detection signal, that contamination has accumulated on said head slider.

19. The electronic component of claim 18 , wherein said one or more sequences of instructions, when executed, further cause performance of:

burnishing said contamination from said head slider.

20. The electronic component of claim 18 , wherein said determining includes determining that said contamination has accumulated on said NFT.