Magnetostriction-driven multiferroicity of MnTe and MnTe/ZnTe epitaxial films

Abstract

Here we demonstrate that MnTe epitaxial films with zinc-blend structure and MnTe/ZnTe multilayers should show ferroelectric polarization in antiferromagnetically (AFM) ordered state and thus belong to multiferroics. Spontaneous ferroelectric polarization results from the bending of highly ionic Mn-Te-Mn bonds induced by magnetostrictive shear strain. Orientation of ferroelectric polarization is coupled with orientation of AFM vector and thus can be controlled by application of the external magnetic field. Due to the clamping of electric and magnetic order parameters, domain structure in MnTe is governed by two mechanisms: depolarizing field produced by electric dipoles and destressing field produced by magnetoelastic dipoles. The values of monodomainization electric and magnetic fields depend upon the sample shape and diminish with the film thickness. Magnetoelectric nature of the domains make it possible to visualize the domain structure by linear and nonlinear optical methods (Kerr effect, second harmonic generation technique).