Computational of localized spinwaves at a stepped surface of an antiferromagnetic metallic monoxide

Abstract

We investigate the spin excitations at the (001) stepped surface in semi-infinite antiferromagnetic monoxide cubic rocksalt structure of the type MO, made up from compounds of metal cations M[Formula: see text] and oxygen anions O[Formula: see text]. At the surface, of semi-infinite monoxide lattices, the translation symmetry along the direction normal to surface zone is broken. Therefore, significant changes of spin dynamics and magnetic properties are expected at the surface in question. The dependence on properties comes from the geometrical arrangement of the chemical species present at the surface, leading to appearing localized antiferromagnetic spin modes. The spin excitations and the amplitudes of precession due to variations in exchange and superexchange parameters generated by the stepped surface zone are simulated and analyzed, for different cases that can be considered, from softening to hardening effects. The technical formalism of matching method, associated to Green functions, is employed to determine the magnonic densities of states, for the spin components of the individual sites that constitute a complete representation of the stepped surface domain boundaries. Our results shown that the calculated localized spin modes are sensitive to the magnetic coupling between different spin sites at the surface. The simulated cases yield criteria under certain experimental conditions, as regards the interpretation of the measurements of the magnetic interactions in the surface zone and its boundaries. However, for a given material, the spin surfaces corresponding to different orientations are not equivalents and, in particular, they do not have the same stability.