Magnetostriction mapping of soft magnetic films on thick rigid substrates

A technique that permits the saturation magnetostriction constant λ to be measured for soft magnetic films that are deposited on thick rigid substrates is reported. Because the technique employs a magnetooptic Kerr sensor for the film magnetization, spatial resolution down to ≃100 μm is easily achieved and maps of λ uniformity can thus be generated. The anisotropy field H_k of a relaxed film at the location of the Kerr-sensor laser spot is measured using the method of Kerr torque magnetometry. The film is then anisotropically stressed by bending the substrate over a rigid stainless-steel knife-edge assembly, and H_k is 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 calculated from the measured ratio of the change in H_k and e and from known constants of film elasticity and saturation magnetization