Doping influence of spin dynamics and magnetoelectric effect in hexagonal Y${}_{0.7}$Lu${}_{0.3}$MnO${}_3$

Abstract

We use inelastic neutron scattering to study spin waves and their correlation with the magnetoelectric effect in Y${}_{0.7}$Lu${}_{0.3}$MnO${}_3$. In the undoped YMnO${}_3$ and LuMnO${}_3$, the Mn trimerization distortion has been suggested to play a key role in determining the magnetic structure and the magnetoelectric effect. In Y${}_{0.7}$Lu${}_{0.3}$MnO${}_3$, we find a much smaller in-plane (hexagonal $ab$-plane) single ion anisotropy gap that coincides with a weaker in-plane dielectric anomaly at $T_N$. Since both the smaller in-plane anisotropy gap and the weaker in-plane dielectric anomaly are coupled to a weaker Mn trimerization distortion in Y${}_{0.7}$Lu${}_{0.3}$MnO${}_3$ comparing to YMnO${}_3$ and LuMnO${}_3$, we conclude that the Mn trimerization is responsible for the magnetoelectric effect and multiferroic phenomenon in Y${}_{1-y}$Lu${}_y$MnO${}_3$.

5 pages, 5 figures