The Microprobe Tester—An Instrument for the Local Evaluation of Magnetic Films

Abstract

The microprobe tester consists of two orthogonal loops wound around a nonconductive probe. One of these loops carries a sinusoidal, high‐frequency current which causes a small local oscillation of the magnetization when the probe is held near the surface of the film. The resulting stray flux induces a voltage in the orthogonal loop. The second harmonic component of this voltage is filtered out and amplified. This second harmonic is used for a precise measurement of the main film parameters. Plots equivalent to B‐H and cross‐loops are obtained, and domain boundaries can be mapped. The instrument is basically inexpensive, insensitive to mechanical vibrations, and its measurements are independent of film reflectivity.