MAGNETOSTRICTION MEASUREMENTS ON THIN-FILMS BY A SLOT-LINE FERROMAGNETIC-RESONANCE TECHNIQUE

We report on a new technique for the determination of the linear magnetostriction constant of thin films. The technique uses the shift in ferromagnetic resonance (FMR) of a magnetostrictive sample upon application of an external stress. A circular thin film is deposited onto a fused quartz plate by ion beam sputter deposition. The plate is mounted in a cantilever configuration, with the film suspended over the junction of a slot-line/coplanar guided structure. The slot line provides a rf magnetic field normal to the film plane, tunable over the frequency range 0.1 GHz<ν<20 GHz. Collinear dc and modulating magnetic fields are applied in the film plane. FMR spectra are obtained by measuring the differential power transmission with respect to modulation field by a phased locked-loop technique. The sample is stressed by deflecting the free end of the cantilever using a micrometer drive. Magnetostriction values are calculated from the measured field shift versus deflection using a model based upon a free-energy expression containing magnetoelastic and magnetic interaction energies. Since this method relies only upon measurement of the FMR field shift, we believe that it is a viable technique for measuring magnetostriction values, especially for very thin films.