DISK SUBSTRATE FOR PERPENDICULAR MAGNETIC RECORDING MEDIUM AND PERPENDICULAR MAGNETIC RECORDING MEDIUM USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a disk substrate for a perpendicular magnetic recording medium exhibiting sufficient productivity, serving the function of a soft magnetic backing layer of the perpendicular magnetic recording medium and scarcely generating noise and to provide the perpendicular magnetic recording medium using such the substrate. SOLUTION: The disk substrate 10 comprises at least a soft magnetic underlayer 2 formed on a nonmagnetic disk-shaped base plate 1 by means of an electroless plating method. The thermal expansion coefficient of the soft magnetic underlayer 2 is larger than a thermal expansion coefficient of the nonmagnetic disk-shaped base plate 1. A saturation magnetostriction constantλs of the soft magnetic underlayer 2 satisfies a relationλs≥-1×10-5. COPYRIGHT: (C)2006,JPO&NCIPI