Patent ID: 8665541
Filing Date: 2014-03-04
Classification: G11B

Abstract:
1. An evaluation method of a perpendicular magnetic recording medium used for information recording of a perpendicular magnetic recording type, comprising: a process of rotating a perpendicular magnetic recording medium, moving a recording head in a radial direction of said perpendicular magnetic recording medium, and recording a first signal of a specific frequency at an arbitrary first position in said perpendicular magnetic recording medium; a process of measuring a reproduction output of said first signal recorded at said first position while moving a reproduction head in the radial direction of said perpendicular magnetic recording medium and by measuring an initial value of a signal/noise ratio of said first signal at a peak position where the reproduction output becomes the maximum; a process of recording a signal of a specific frequency by using said recording head at a second position away from said first position by a predetermined distance in the radial direction of said perpendicular magnetic recording medium; a process of measuring the signal/noise ratio of said first signal at said peak position again; a process of repeating the process of recording the signal of the specific frequency at a position brought close to said first position from said second position by a predetermined distance using said recording head and of measuring the signal/noise ratio of said first signal at said peak position again while sequentially getting closer to said first position from said second position; and a process of determining whether the value of the measured signal/noise ratio has lowered from the initial value by a predetermined range or more.