The present invention relates to the structure of a main pole of a magnetic head for perpendicular recording, a process of manufacturing the same and a magnetic recording disk apparatus using the same.
One possible approach to increasing the areal recording density of a magnetic disk is to use a perpendicular recording method, instead of the conventional in-plane magnetic recording method. In magnetic perpendicular recording, the recorded magnetization formed in a recording medium is perpendicular to the film face. This recording method offers an advantage in that microscopic recorded magnetization is thermally stable. A magnetic head for perpendicular recording may be a write/read dual element head, in which use should be made of a magnetoresistive effect type head as a read head and a single-pole type head, consisting of a main pole and an auxiliary pole, as a write head. In the single-pole type head, a magnetic field necessary for recording is generated from the main pole, which is tailored to the recording track width. For this reason, the shape of the main pole on the head surface facing the recording medium largely affects the distribution of recorded magnetization. It can be demonstrated, for example, by comparison between the case of FIG. 1A and the case of FIG. 1B. In the case of FIG. 1A, in which a main pole 12 is shown as a rectangle which is determined by the track width and pole thickness, and the angle formed by the direction perpendicular to a recording track 11 and the main pole's cross-track direction, namely what is called a “yaw angle,” is O degree, writing (recording) is effected depending on the width of the downstream edge of the main pole in a medium moving direction 15, and thus no side writing occurs. On the other hand, in the case of FIG. 1B, in which there is a yaw angle, a considerable amount of side writing 13 will occur, depending on the main pole edge in the direction of the thickness. As an attempt to prevent such side writing, a trapezoidal main pole 12 has been used, as illustrated in FIG. 1C and FIG. 1D. In other words, the main pole's downstream edge, in the medium moving direction 15, and its neighboring side edge crossing it form an acute angle. Reference to this type of main pole has been made, for example, in JP-B No. 286842/2000 and Digests of PMRC 2000 (2000) pp. 131–132.
The above-mentioned shape, which is intended to decrease the amount of side writing in a situation that there is a yaw angle, has the following problem: since the pole thickness is smaller at the track edge, the head's recording performance is lower in an area nearer to the track edge, and, thus, the effective track width decreases. This is a barrier to improvement in the track density.