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

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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.