Magnetostriction Mapping of Soft Magnetic Films on Thick Rigid Substrates

A new technique is reported that permits the saturation magnetostriction constant λ to be measured for soft magnetic films that are deposited on thick rigid substrates. Because the technique employs a magneto-optic Kerr sensor of the film magnetization, spatial resolution down to ~100µm is easily achieved, and maps of λ uniformity can thus be generated. The anisotropy field Hkof a relaxed film at the location of the Kerr sensor laser spot is measured using the method of Kerr Torque Magnetometry (KTM). The film is then anisotropically stressed by bending the substrate over a rigid stainless steel knife edge assembly, and Hkis again measured. The strain (e) induced in the film by the bending is measured by a simple laser-beam deflection technique. The sign and magnitude of λ are then calculated from the measured ratio of the change in Hkand e and from known constants of film elasticity and saturation magnetization. © 1990 IEEE