Programme

I.2 -- Invited, VCTP-44

Date: Monday, 29 July 2019

Time: 10:30 - 11:00

Spin Waves and Skyrmions in Magneto-Ferroelectric Superlattices

H. T. Diep (1) and I. Sharafullin (2)

(1) Laboratoire de Physique Théorique et Modélisation Université de Cergy-Pontoise, CNRS, UMR 8089, 2 Avenue Adolphe Chauvin, 95302 Cergy-Pontoise, Cedex, France; (2) Bashkir State University, 32, Validy str, 450076, Ufa, Russia.

We present in this talk the effects of Dzyaloshinskii-Moriya (DM) magnetoelectric coupling between ferroelectric and magnetic layers in a superlattice formed by alternate magnetic and ferroelectric films. Magnetic films are modelized with the Heisenberg spins interacting with each other via an exchange J and a DM interaction with the ferroelectric interface. Electrical polarizations are assumed to be spins of Ising type occupying the lattice sites in the ferroelectric films. We determine the ground-state (GS) spin configuration in the magnetic film. In zero applied magnetic field, the GS is periodically non collinear. In an applied field H perpendicular to the superlattice layers, we show the existence of skyrmions at the interface. Using the Green's function method we study the spin waves (SW) excited in the magnetic layer sandwiched between two ferroelectric films, in zero field. We show that the DM interaction strongly affects the long-wave length SW mode, changing from ferromagnetic behavior to antiferromagnetic one with increasing DM interaction. We also calculate the zero-point spin contraction at temperature T=0 and the magnetization at low T. In an applied magnetic field H where skyrmions appear, we use Monte Carlo simulations to calculate various physical quantities at finite temperatures such as the critical temperature, the layer magnetization and the layer polarization, as functions of the magnetoelectric DM coupling and H. Phase transition to the disordered phase is studied in detail.

Presenter: Diep The Hung