Patent ID: 8937785
Filing Date: 2015-01-20
Classification: G11B

Abstract:
1. A magnetic disk apparatus comprising: a magnetic disk; a slider including a head element configured to record or read data on or from the magnetic disk; a heater provided in the slider and configured to heat the slider upon receipt of power and to vary a protrusion amount of the head element toward the magnetic disk by heat deformation of the slider due to heating; a controller configured to perform DFH control to vary a control amount for power applied to the heater at a fixed period of time; a sensor provided in the slider and configured to output a signal corresponding to the protrusion amount of the head element, which corresponds to the DFH control; and a determination unit configured to determine a touchdown of contact between the magnetic disk and part of the slider, based on a peak value of a DC output signal that is a direct current output component of the sensor, which corresponds to the DFH control, wherein the control amount for the DFH control includes a pulse string of the fixed period of time and a predetermined amplitude, and the determination unit determines the touchdown, based on values at peak points of the output signal of the sensor which are close to points of variation in level in a predetermined direction of the pulse string, respectively.