Control method for magnetic disk device, magnetic disk device, and magnetic disk

1. A magnetic disk device including:

a magnetic disk possessing a track in which a plurality of magnetic elements magnetically separated from each other are arranged in a predetermined array period;

a magnetic head which follows the track and writes data upon receiving a recording signal possessing a time period corresponding to an array period of the plurality of magnetic elements; and

a control circuit configured to perform a control method, the control method comprising:

writing the data by varying a phase of the array period of the plurality of magnetic elements or a phase of the time period of the recording signal in one section of the track from a corresponding phase in another section of the track;

reading a reproduction signal from the track; and

determining a phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal, based on a reproduction signal read from the one section and a reproduction signal read from the other section,

wherein the determining the phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal is performed, based on a magnitude of a relation between the amplitude of the reproduction signal read from the one section and the amplitude of the reproduction signal read from the other section.

2. The magnetic disk device of claim 1 , wherein the writing the data is performed with the recording signal of which a level is reversed at every unit time period.

3. The magnetic disk device of claim 1 , wherein the phase of the array period of the plurality of magnetic elements or the phase of the time period of the recording signal in the one section is different from the corresponding phase in the other section by a half period.

4. The magnetic disk device of claim 1 , wherein the determining the phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal is performed, based on amplitude of the reproduction signal read from the one section and amplitude of the reproduction signal read from the other section.

5. The magnetic disk device of claim 1 , wherein the presence or absence of the phase shift between the array period of the magnetic elements and the time period of the recording signal is determined, based on whether a difference greater than a predetermined magnitude exists between the amplitude of the reproduction signal read from the one section and the amplitude of the reproduction signal read from the other section.

6. The magnetic disk device of claim 1 , wherein when the phase shift is determined, the determining the phase shift is performed again after updating the phase of the time period of the recording signal.

7. The magnetic disk device of claim 1 , wherein information on the phase of the time period of the recording signal is stored in a storage unit, the phase being determined based on the determination result of the phase shift.

8. The magnetic disk device of claim 7 , wherein the phase of the time period of the recording signal to be outputted to the magnetic head is set based on the information stored in the storage unit.

9. The magnetic disk device of claim 7 , wherein the reproduction signal is read from the track in which the data is written by varying the phase of the array period of the plurality of magnetic elements or the phase of the time period of the recording signal in each of a plurality of sections, and wherein the phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal is determined, based on the reproduction signal read out from each of the plurality of sections.

10. A magnetic disk device including:

a magnetic disk possessing a track in which a plurality of magnetic elements magnetically separated from each other are arranged in a predetermined array period;

a magnetic head which follows the track and writes data upon receiving a recording signal possessing a time period corresponding to an array period of the plurality of magnetic elements; and

a control circuit configured to perform a control method, the control method comprising:

writing the data by varying a phase of the array period of the plurality of magnetic elements or a phase of the time period of the recording signal in one section of the track from a corresponding phase in another section of the track;

reading a reproduction signal from the track; and

determining a phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal, based on a reproduction signal read from the one section and a reproduction signal read from the other section,

wherein the presence of the phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal is determined, based on whether one of: the amplitude of the reproduction signal read from the one section and the amplitude of the reproduction signal read from the other section, is greater than a first threshold and the other amplitude is less than a second threshold which is smaller than the first threshold.

11. The magnetic disk device of claim 10 , wherein the writing the data is performed with the recording signal of which a level is reversed at every unit time period.

12. The magnetic disk device of claim 10 , wherein the phase of the array period of the plurality of magnetic elements or the phase of the time period of the recording signal in the one section is different from the corresponding phase in the other section by a half period.

13. The magnetic disk device of claim 10 , wherein the determining the phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal is performed, based on amplitude of the reproduction signal read from the one section and amplitude of the reproduction signal read from the other section.

14. The magnetic disk device of claim 10 , wherein information on the phase of the time period of the recording signal is stored in a storage unit, the phase being determined based on the determination result of the phase shift.

15. A magnetic disk device including:

a magnetic disk possessing a track in which a plurality of magnetic elements magnetically separated from each other are arranged in a predetermined array period;

a magnetic head which follows the track and writes data upon receiving a recording signal possessing a time period corresponding to an array period of the plurality of magnetic elements; and

a control circuit configured to perform a control method, the control method comprising:

writing the data by varying a phase of the array period of the plurality of magnetic elements or a phase of the time period of the recording signal in one section of the track from a corresponding phase in another section of the track;

reading a reproduction signal from the track; and

determining a phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal, based on a reproduction signal read from the one section and a reproduction signal read from the other section,

wherein the presence of the phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal is determined, based on an error rate of the reproduction signal read from the one section and an error rate of the reproduction signal read from the other section.

16. The magnetic disk device of claim 15 , wherein the writing the data is performed with the recording signal of which a level is reversed at every unit time period.

17. The magnetic disk device of claim 15 , wherein the phase of the array period of the plurality of magnetic elements or the phase of the time period of the recording signal in the one section is different from the corresponding phase in the other section by a half period.

18. The magnetic disk device of claim 15 , wherein the determining the phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal is performed, based on amplitude of the reproduction signal read from the one section and amplitude of the reproduction signal read from the other section.

19. A magnetic disk device including:

a magnetic disk possessing a track in which a plurality of magnetic elements magnetically separated from each other are arranged in a predetermined array period;

a magnetic head which follows the track and writes data upon receiving a recording signal possessing a time period corresponding to an array period of the plurality of magnetic elements; and

a control circuit configured to perform a control method, the control method comprising:

writing the data by varying a phase of the array period of the plurality of magnetic elements or a phase of the time period of the recording signal in one section of the track from a corresponding phase in another section of the track;

reading a reproduction signal from the track; and

determining a phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal, based on a reproduction signal read from the one section and a reproduction signal read from the other section,

wherein when the phase shift is determined, the determining the phase shift is performed again after updating the phase of the time period of the recording signal,

wherein increase and decrease of the phase of the time period of the recording signal is determined, based on a magnitude of a relation between the amplitude of the reproduction signal before the updating and the amplitude of the reproduction signal after the updating.

20. A magnetic disk device including:

a magnetic disk possessing a track in which a plurality of magnetic elements magnetically separated from each other are arranged in a predetermined array period;

a magnetic head which follows the track and writes data upon receiving a recording signal possessing a time period corresponding to an array period of the plurality of magnetic elements; and

a control circuit configured to perform a control method, the control method comprising:

writing the data by varying a phase of the array period of the plurality of magnetic elements or a phase of the time period of the recording signal in one section of the track from a corresponding phase in another section of the track;

reading a reproduction signal from the track; and

determining a phase shift between the array period of the plurality of magnetic elements and the time period of the recording signal, based on a reproduction signal read from the one section and a reproduction signal read from the other section,

wherein when the phase shift is determined, the determining the phase shift is performed again after updating the phase of the time period of the recording signal,

wherein an amount of updating of the phase of the time period of the recording signal is determined, based on a magnitude of a relation between the amplitude of the reproduction signal read from the one section and the amplitude of the reproduction signal read from the other section.