A fast scanning magneto-optic Kerr M-H hysteresigraph for thin film media

An automated, scanning magnetometer that permits spatially resolved measurements of longitudinal magnetic properties to be made nondestructively on thin-film disks used for data storage is described. The magnetization of a 2-mm-diameter spot on a thin-film disk is monitored by the magnetooptic Kerr effect while a magnetic field is swept in the plane of the film. The M-H response of the magnetic film at a prescribed location can be measured in 1200 ms for a swept-field amplitude of ±8 kOe. A PS/2 computer controls the swept field and R-θ position of the disk while simultaneously capturing and digitizing the Kerr response and the applied field strength. While the disk is translated from one location to the next, the PS/2 analyzes the hysteresis loop for the local coercivity, squareness, and coercivity squareness. The full hysteresis loops, in addition to these magnetic parameters, can be acquired for 100 locations in just under 3 min