Patent ID: 7848049
Filing Date: 2010-12-07
Classification: G11B

Abstract:
1. A magnetic disk apparatus comprising: a magnetic disk provided with a data recording area and a servo-pattern area, the data recording area being provided by a non-magnetic area scattered with magnetic regions, the servo-pattern area including a plurality of magnetic regions each having a larger area than the magnetic regions in the data recording area and pre-magnetized in a uniform magnetization direction; a magnetic head arranged to reciprocate radially of the magnetic disk for giving a magnetization direction to the magnetic regions in the data recording area and for reading a magnetization direction of the magnetic regions in the data recording area and of the magnetic regions in the servo-pattern area; a reverse-pulse detector for reading the servo-pattern area with the magnetic head before recording or reproducing with respect to the data recording area, the reverse-pulse detector being arranged to detect, from servo reproduction signal pulses obtained from magnetic directions in the magnetic regions of the servo-pattern area, a reverse pulse corresponding to reversal of magnetization direction relative to the uniform magnetization direction; and a re-magnetizer for causing the magnetic head to perform re-magnetizing of the magnetic regions in the servo-pattern area when a count of reverse pulses is not smaller than a threshold number.