Love-type surface-acoustic waves propagating in amorphous iron-boron films with multilayer structure

The propagation of Love-type surface-acoustic waves (SAWs) in a multilayer structure was investigated. The structures consisted of rf-sputtered iron-boron (FeB) amorphous magnetic films stacked alternatively to SiOx insulating layers i.e., FeB-(SiOx−FeB)×n (where n denotes the stacking number) onto a soft glass substrate. The phase of waves was controlled over a wide range by a magnetic field applied in the film plane, through change in the strength of magnetoelastic coupling between the magnetic moment of the FeB film and SAW propagating in the substrate. The transducers for the Love-type SAW excitation were constructed by combining the interdigital electrodes and ZnO films, prepared by sputtering in an oblique electrode arrangement. The controllable phase shift (ΔΦ) under a magnetic field increases linearly with n, when the total FeB film thickness DM is kept constant (DM=1.5 μm). The ΔΦ of a device with n=8 is about 2300°/cm within the magnetic field smaller than about 120 Oe.