Abstract: In a perpendicular magnetic recording medium, a soft magnetic film playing the role of an back layer, but not having a domain wall structure, is positioned beneath a perpendicular magnetization film. Such a back layer improves the envelope characteristic of the medium at the time of recording and reproduction. Moreover, the medium is free from spike noise and the decrease or cancellation of recorded magnetization ascribable to the movement of the domain wall of a back layer. The medium of the present invention is therefore a drastic solution to the problems particular to a conventional perpendicular magnetic recording medium and realizes desirable recording and reproducing characteristics.

Abstract: A magnetic disk drive for recording and reproducing data out of a magnetic disk with a magnetoresisive (MR) head contacting the disk is disclosed. When the MR device is spaced from the surface of the medium by a recess of less than 15 nm inclusive, the surface of the medium is provided with a sheet resistance of less than 5 &OHgr;/cm2 inclusive. When the sheet resistance is greater than 5 &OHgr;/cm2, the recess is selected to be 16 nm or above. To enhance a frequency characteristic, the surface of the disk is provided with an undulation period of greater than 2 &mgr;m inclusive in the direction of movement of a head and a surface roughness of less than 1 nm inclusive. With this configuration, the disk drive obviates electrical faults ascribable to the sliding contact of the head and disk.

Abstract: The present invention provides a magnetic disc apparatus comprising a vertical two-layered magnetic recording (MR) medium and a mono-pole/MR composite head or ID/MR composite head, wherein the vertical two-layered magnetic recording medium includes a vertical magnetization film formed on an undercoat soft magnetic film having no magnetic domain wall structure. This eliminates the fatal defect of a conventional vertical two-layered medium that an undercoat soft magnetic film domain wall is easily shifted by an external magnetic field generated by motors for disc rotation and head positioning, causing demagnetization of the recording magnetization to lower the output. The magnetic disc apparatus according to the present invention enables to obtain a high output stability.

Abstract: In the recorded magnetization state measurement method of this invention, a recorded magnetization pattern formed on a medium is first detected by a magnetic force microscope (MFM). An MFM output signal extractor then extracts a one-dimensional MFM output signal along the direction of recording at a prescribed MFM reproduction width from the recorded magnetization pattern detected by the magnetic force microscope. A waveform value analyzer then calculates as output reproduction the average value of amplitude of the MFM output signal extracted by the MFM output signal extractor and calculates as medium noise the standard deviation of amplitude of the MFM output signal.