Measurements of crystalline anisotropy on longitudinal media

Abstract

The crystalline anisotropy constant in both thin film and particulate recording media has been determined utilizing high field torque measurements and transmission electron microscopy (TEM). Extrapolation of torque measurements at 45/spl deg/ to the film plane yields a "infinite field torque" that depends solely on the anisotropy constant, the distribution of easy axes, and the saturation magnetization. The distribution of easy axes was determined by TEM measurements. Using this technique the crystalline anisotropy constant of a CoCrTa thin film disk (M/sub 8/=690 emu/cc) was found to be 2.2/spl times/10/sup 6/ erg/cc. A floppy disk with Co-/spl gamma/Fe/sub 2/O/sub 3/ particles (M/sub 8/=120 emu/cc) yielded crystalline anisotropy constant of approximately 6.0/spl times/10/sup 5/ erg/cc.