Perpendicular magnetic recording media and magnetic disc apparatus

1. A perpendicular magnetic recording medium for a shingle-type recording by a magnetic head, comprising:

a base; and

a laminated film including a soft magnetic ground layer and a recording layer formed on the base,

wherein, the soft magnetic ground layer has a thickness in a range of more than 0 nm to 40 nm and the thickness is based upon a core width of the magnetic head for recording and reproduction with respect to the perpendicular magnetic recording medium, and the perpendicular magnetic recording medium has a track pitch narrower than the core width of the magnetic head.

2. The perpendicular magnetic recording medium according to claim 1 , wherein

the perpendicular magnetic recording medium is a medium for thermomagnetic recording.

3. A perpendicular magnetic recording medium for a shingle recording type having a laminated film including a soft magnetic ground layer and a recording layer formed on a base, the soft magnetic ground layer having a thickness based upon a core width of a magnetic head for recording and reproduction with respect to the perpendicular magnetic recording medium and a track pitch narrower than the core width, wherein

the thickness of the soft magnetic ground layer is thinner than a thickness of a soft magnetic ground layer of a perpendicular magnetic recording medium for use in a recording type with a track pitch wider than the core width of the magnetic head by 2×d×A (nm),

wherein,

d =the core width of the magnetic head- TP _shingle, and

A =( Bs — mp/Bs — sul )×( SUL _conv/TP — conv ),

wherein,

TP_shingle: the track pitch of the perpendicular magnetic recording medium for the shingle recording type;

Bs_mp: saturation magnetic flux density of a main pole of the perpendicular magnetic recording medium for the shingle recording type;

Bs_sul: saturation magnetic flux density of the soft magnetic ground layer of the perpendicular magnetic recording medium for the shingle recording type;

SUL_conv: a thickness of the soft magnetic ground layer required for saturation of Spi-SNR in the perpendicular magnetic recording medium for a recording type with the track pitch wider than the core width of the magnetic head; and

TP_conv: the track pitch of the perpendicular magnetic recording medium for the recording type with the track pitch wider than the core width of the magnetic head.

4. A magnetic disk device comprising:

the perpendicular magnetic recording medium according to claim 1 ,

a magnetic head for writing information in the perpendicular magnetic recording medium, and

a control unit for controlling a write operation on the perpendicular magnetic recording medium of the magnetic head.

5. A magnetic disk device comprising:

a perpendicular magnetic recording medium having a soft magnetic ground layer,

a magnetic head for writing information in the perpendicular magnetic recording medium, and

a control unit for controlling a write operation on the perpendicular magnetic recording medium of the magnetic head,

wherein a core width of the magnetic head is wider than a track pitch of the perpendicular magnetic recording medium, and the soft magnetic ground layer has a thickness based upon a core width of the magnetic head and a track pitch narrower than the core width,

wherein the thickness of the soft magnetic ground layer is thinner than a thickness of a soft magnetic ground layer of a perpendicular magnetic recording medium for use in a recording type with a track pitch wider than the core width of the magnetic head by 2×d×A (nm),

wherein,

d =the core width of the magnetic head- TP _shingle, and

A =( Bs — mp/Bs — sul )×( SUL _conv/TP — conv ),

wherein,

TP_shingle: the track pitch of the perpendicular magnetic recording medium for the shingle recording type;

Bs_mp: saturation magnetic flux density of a main pole of the perpendicular magnetic recording medium for the shingle recording type;

Bs_sul: saturation magnetic flux density of the soft magnetic ground layer of the perpendicular magnetic recording medium for the shingle recording type;

SUL_conv: a thickness of the soft magnetic ground layer required for saturation of Spi-SNR in the perpendicular magnetic recording medium for a recording type with the track pitch wider than the core width of the magnetic head; and

TP_conv: the track pitch of the perpendicular magnetic recording medium for the recording type with the track pitch wider than the core width of the magnetic head.

6. The magnetic disk device according to claim 5 , wherein

heating means is included that heats the perpendicular magnetic recording medium before writing of a recording bit.

7. The perpendicular magnetic recording medium according to claim 3 , wherein

the perpendicular magnetic recording medium is a medium for thermomagnetic recording.

8. A magnetic disc apparatus comprising:

a magnetic head for recording and reproduction, and

a perpendicular magnetic recording medium for a shingle-type recording by the magnetic head, said magnetic recording medium comprising:

a base; and

a laminated film including a soft magnetic ground layer and a recording layer formed on the base,

wherein, the soft magnetic ground layer has a thickness based upon a core width of the magnetic head with respect to the perpendicular magnetic recording medium and has a track pitch narrower than the core width,

wherein, the thickness of the soft magnetic ground layer is thinner than a thickness of a soft magnetic ground layer of a perpendicular magnetic recording medium for use in a recording type with a track pitch wider than the core width of the magnetic head by 2×d×A (nm),

wherein,

d =the core width of the magnetic head- TP _shingle, and

A =( Bs — mp/Bs — sul )×( SUL — conv/TP — conv ),

wherein,

TP_shingle: the track pitch of the perpendicular magnetic recording medium for the shingle recording type;

Bs_mp: saturation magnetic flux density of a main pole of the perpendicular magnetic recording medium for the shingle recording type;

Bs_sul: saturation magnetic flux density of the soft magnetic ground layer of the perpendicular magnetic recording medium for the shingle recording type;

SUL_conv: a thickness of the soft magnetic ground layer required for saturation of Spi-SNR in the perpendicular magnetic recording medium for a recording type with the track pitch wider than the core width of the magnetic head; and

TP_conv: the track pitch of the perpendicular magnetic recording medium for the recording type with the track pitch wider than the core width of the magnetic head.