Abstract: Embodiments in accordance with the present invention control pitch variations that are not observed in self servo write (SSW). According to one embodiment of the present invention, an outer radius side area of a magnetic disk is erased using an external magnetic field, and an inner radius side area is subjected to self erase using a head. The magnetization state in the base of the inner radius side area is different from that of the outer radius side area before pattern writing. Therefore, in the inner radius side area and the outer radius side area, even if a radial pattern of the same pitch is read, the different APCs are measured. With SSW of this embodiment, a reference APC used in the inner radius side area is different from that used in the outer radius side area. In this manner, the pitch variation is prevented.