Magnetic disk apparatus and recording method

1. A magnetic disk apparatus comprising:

a computing unit that obtains data to be recorded on a magnetic disk and computes an intermediate bit length based on a longest bit length and a shortest bit length of bit lengths of the obtained data;

an adjusting unit that adjusts a strength of a recording current for recording the obtained data based on a difference between the intermediate bit length and a bit length of the obtained data; and

a recording unit that repeatedly detects an error rate for recording data by using the adjusted recording current while narrowing down a track width on the magnetic disk and records the obtained data with a track width corresponding to an error rate detected immediately before an error rate that is detected to be equal to or greater than a predetermined value.

2. The magnetic disk apparatus according to claim 1 , wherein the recording unit

changes the track width for the detection based on a change width obtained by dividing a standard track width of the magnetic disk by a predetermined number;

records the data on a plurality of tracks by using the adjusted recording current; and

detects the error rate by detecting an error rate of data recorded on a part of the plurality of tracks.

3. The magnetic disk apparatus according to claim 1 , wherein

the computing unit computes a difference between the longest bit length and the shortest bit length, and

the adjusting unit adjusts the recording current by a value obtained by dividing an initial value of the recording current by the difference.

4. The magnetic disk apparatus according to claim 1 , further comprising:

an extracting unit that extracts a frequency component of the data to be recorded on the magnetic disk; and

a recording current management unit that associates the frequency component with a bit length and records a plurality of types of combinations of the bit length and a recording current, wherein

the recording unit adjusts the strength of the recording current based on a result of the extraction by the extracting unit and information managed by the recording current managing unit.

5. A recording method carried out by a magnetic recording apparatus that records data on a magnetic disk, the method comprising:

obtaining data to be recorded on a magnetic disk;

computing an intermediate bit length based on a longest bit length and a shortest bit length of bit lengths of the obtained data;

adjusting a strength of a recording current for recording the obtained data based on a difference between the intermediate bit length and a bit length of the obtained data; and

repeatedly detecting an error rate for recording data by using the adjusted recording current while narrowing down a track width on the magnetic disk and recording the obtained data with a track width corresponding to an error rate detected immediately before an error rate that is detected to be equal to or greater than a predetermined value.

6. The recording method according to claim 5 , further comprising:

changing the track width for the detection based on a change width obtained by dividing a standard track width of the magnetic disk by a predetermined number;

recording the data on a plurality of tracks by using the adjusted recording current; and

detecting the error rate by detecting an error rate of data recorded on a part of the plurality of tracks.

7. The recording method according to claim 5 , further comprising:

computing a difference between the longest bit length and the shortest bit length; and

adjusting the recording current by a value obtained by dividing an initial value of the recording current by the difference.

8. The recording method according to claim 5 , further comprising:

extracting a frequency component of the data to be recorded on the magnetic disk;

associating the frequency component with a bit length and recording a plurality of types of combinations of the bit length and a recording current; and

adjusting the strength of the recording current based on a result of the extraction of the frequency component and the recorded information.