Microwave-assisted magnetic recording device and method using non-constant microwave

1. A magnetic recording device, comprising:

a magnetic disk;

a magnetic head that performs magnetic recording to the magnetic disk, including:

main magnetic pole layer that generates a recording magnetic field synchronizing a recording current generated by recording voltage corresponding to recording signals and that applies the recording magnetic field to the magnetic disk; and

a microwave generating element that is arranged in a vicinity of the main magnetic pole layer and that applies a microwave magnetic field to the magnetic disk during magnetic recording; and

a microwave generating element driving current control circuit

that, during the magnetic recording, applies a microwave generating element driving current at a first current level to the microwave generating element for a period that is from at the latest a polarity reversal of the recording current before a subsequent polarity reversal of the recording voltage, and thereafter

that applies another microwave generating element driving current at a second current level, which is smaller than the first current level, to the microwave generating element, until the polarity reversal of the recording voltage.

2. The magnetic recording device according to claim 1 , wherein

the microwave generating element driving current control circuit applies the microwave generating element driving current at the first current level in synchronization with the polarity reversal of the recording voltage.

3. The magnetic recording device according to claim 1 , wherein

the microwave generating element driving current control circuit applies the microwave generating element driving current at the first current level in synchronization with the polarity reversal of the recording current.

4. The magnetic recording device according to claim 1 , wherein

the microwave generating element driving current control circuit applies the microwave generating element driving current at the first current level after a passage of a predetermined delay time duration from the polarity reversal of the recording voltage to compensate a phase difference between the recording voltage and the recording current.

5. The magnetic recording device according to claim 1 , wherein

the microwave generating element driving current control circuit applies the microwave generating element driving current at the first current level for a time duration or more, the time duration being required to saturate an increase of a magnetization reversal probability of a portion of the magnetic disk to which the recording magnetic field is applied.

6. A magnetic recording method, comprising:

generating a recording current by a recording voltage corresponding to a recording signal;

generating a recording magnetic field synchronizing the recording current; and

applying the recording magnetic field and a microwave magnetic field simultaneously to a predetermined region of a magnetic disk so that magnetic recording to the magnetic disk is performed, wherein

during the magnetic recording, a microwave generating element driving current at a first current level is applied to the microwave generating element for a period that is from at the latest a polarity reversal of the recording current before a subsequent polarity reversal of the recording voltage, and thereafter,

another microwave generating element driving current at a second current level, which is smaller than the first current level, is applied to the microwave generating element or the application of the another microwave generating element driving current is stopped until the polarity reversal of the recording voltage.

7. The magnetic recording method according to claim 6 , wherein

the microwave generating element driving current at the first current level is applied in synchronization with the polarity reversal of the recording voltage.

8. The magnetic recording method according to claim 6 , wherein

the microwave generating element driving current at the first current level is applied in synchronization with the polarity reversal of the recording current.

9. The magnetic recording method according to claim 6 , wherein

the microwave generating element driving current at the first current level is applied after a passage of a predetermined delay time duration from the polarity reversal of the recording voltage to compensate a phase difference between the recording voltage and the recording current.

10. The magnetic recording method according to claim 6 , wherein

the microwave generating element driving current at the first current level is applied for a time duration or more, the time duration being required to saturate an increase of a magnetization reversal probability of a portion of the magnetic disk to which the recording magnetic field is applied.

11. The magnetic recording device according to claim 1 , wherein

the microwave generating element driving current is an alternating current, and

the microwave generating element driving current at the first current level is positively and negatively symmetric.

12. The magnetic recording device according to claim 1 , wherein

the microwave generating element driving current is an alternating current, and

the microwave generating element driving current at the second current level is positively and negatively symmetric.

13. The magnetic recording method according to claim 6 , wherein

the microwave generating element driving current is an alternating current, and

the microwave generating element driving current at the first current level is positively and negatively symmetric.

14. The magnetic recording method according to claim 6 , wherein

the microwave generating element driving current is an alternating current, and

the microwave generating element driving current at the second current level is positively and negatively symmetric.