Patent ID: 7474493

Claim:
A magnetic disk apparatus comprising: a perpendicular disk recording medium having a plurality of tracks disposed thereon concentrically or helically on a layer plane of said medium and having servo areas that cross the plurality of tracks radially on which a servo pattern for decoding a head position signal is disposed with magnetization information in a direction perpendicular to the layer plane; a motor for rotationally driving the perpendicular magnetic disk recording medium; a magnetic head on which a single magnetic pole type write element having a main pole and a return pole and a read element are mounted; an actuator for controlling the position of the magnetic head on the perpendicular magnetic recording medium; a servo decoder for receiving the read signal from the read element to generate the head position signal; and a servo circuit for receiving a signal from the servo decoder to supply a driving signal to the actuator, wherein the servo pattern includes a plurality of burst-signal areas on which magnetizations of a positive direction and magnetizations of a negative direction are perpendicular to the layer plane and disposed alternately in a down-track direction and a plurality of DC-signal areas disposed adjacent in a disk radius direction to the plurality of burst-signal areas, and each DC-signal area is formed of combination of a DC-signal of a positive magnetization direction and a DC-signal of a negative magnetization direction both of which are perpendicular to the layer plane, the burst-signal areas are disposed by a combination of positive and negative magnetizations so that the sum of the magnetizations of the burst-signal areas is almost 0, the DC-signal areas are disposed by a combination of positive and negative magnetizations so that the sum of the magnetizations of an area in a range equivalent to a width of the return pole of the single magnetic pole type write element is approximately 0, said each DC-signal area is formed by a combination of only one DC-signal of a positive magnetization direction and only one DC-signal of a negative magnetization direction, the DC-signal of positive magnetization direction and the DC-signal of negative magnetization direction have almost the same area, and the magnetization direction of the DC-signal adjacent to the inner side in a disk radius direction of the burst-signal area is opposite to the magnetization direction of the DC-signal adjacent to the outer side in the disk radius direction of the burst-signal area, and the sum of the magnetizations of the DC-signal areas corresponding to a width of the return pole of the single magnetic pole type write element is approximately 0, when a sum of magnetization of DC-signal areas is reversed in a disk radius direction at a period of half of the width of the return pole.