Magnetoelastic surface waves in a magnetic film–piezoelectric substrate configuration

Abstract

This paper treats the propagation characteristics of magnetoelastic surface waves in a delay line consisting of a ferromagnetic film deposited on a piezoelectric substrate. Magnetoelastic coupling within the film and mechanical coupling between the film and substrate enables the acoustic velocity to be varied by changing the magnetic bias field. A theory to predict the dependence of the surface wave velocity upon applied dc magnetic field, material constants, and frequency is presented. The velocity change occurs predominantly in a bias field range where the static magnetization vectors are undergoing a rotation. The two orientations of the magnetic field in the sagittal plane considered exhibit significantly different characteristics. With the field parallel to the direction of propagation the velocity first decreases, attains a minimum, and then increases toward a saturation value as the external field is increased. With the field normal to the plane of the film, the velocity increases monotonically toward a saturation value with an increase in field. The calculated velocity changes are in good agreement with changes measured on a Ni-LiNbO3 delay line.