Propagation of surface magnetoelastic waves in TmFeO₃ at the spin reorientation

Experimental and theoretical studies of the propagation of surface magnetoelastic waves at the spin reorientation of TmFeO₃ are presented. It was found that surface waves propagating on the (a-b) surface and along the a axis of the orthorhombic crystal, exhibit velocity dips ΔV/V⁰2.5% at the transition temperatures of the spin reorientation. A magnetic field applied in the reorientation plane suppresses and/or shifts the velocity dips. Similar effects were previously observed for shear bulk waves. The observed results are accounted for by using phenomenological magnetic and magnetoelastic expressions in the coupled equations of motion. It is concluded that the surface acoustic wave interacts with the antiferromagnetic modes of the bulk.