Abstract
The propagation of bulk and surface magnetoacoustic waves is studied in paramagnetic materials on the basis of a phenomenological, fully nonlinear, rotationally invariant, thermodynamically admissible theory of the magnetoelasticity of insulators such as rare‐earth compounds. The work is self‐contained and develops from basic nonlinear equations to solve for propagation modes after linearization of both volume and surface equations about a bias state in accordance with the methods of nonlinear continuum mechanics. The initial nonlinear feature of the theory, associated with rotational invariance, allows one to place in evidence the effects of a bias magnetic field on the dynamical properties of the medium. In particular, among the effects thus exhibited are (1) a symmetry breaking favoring the existence of magnetoelastic couplings (biased piezomagnetism), which would not exist in the absence of bias fields, (2) an alteration in the bulk‐wave speeds (direct magnetoacoustic effects), (3) an acoustical linear birefringence, and (4) in addition to the classical Rayleigh mode, creation of an SH magnetoacoustic surface mode akin to the Bleustein–Gulyaev mode of acoustoelectricity, results from adequate symmetry breaking effects of the bias magnetic field. The influence of viscosity and magnetic relaxation is also examined.
Published Version
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