The measurement of magnetostriction constants of thin films using planar microwave devices and ferromagnetic resonance

Abstract

In this paper we introduce a new technique for measuring the saturation magnetostriction constant (λs) for isotropic polycrystalline thin films. The technique makes use of nonresonant planar microwave structures together with a novel stressing mechanism to induce a shift in the resonant field of a magnetic thin film as measured by a ferromagnetic resonance (FMR) experiment. Measurement of the shift induced by a uniaxial stress allows for determination of λs via a magnetic resonance analysis. Either a slotline device or coplanar waveguide (CPW) was used as the source of the microwave excitation field depending upon the orientation of the dc magnetic field. To evaluate the technique, polycrystalline Ni films of thickness of 637 nm were sputtered onto glass substrates at room temperature for comparison with the literature. Using a 50-Ω CPW, FMR measurements at 9 GHz revealed an average value of λs of −36×10−6 a value in agreement with those previously reported. The technique provides increased flexibility over other FRM techniques as it is wideband and directly accessible.