Perpendicular magnetic recording media and magnetic disc apparatus

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.

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.

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.