Neutron Scattering Studies of the Ferroelectric Distortion and Spin Dynamics in the Type-1 Multiferroic Perovskite Sr0.56Ba0.44MnO3

TL;DR

This study uses neutron and x-ray scattering to explore the interplay of ferroelectricity and spin dynamics in Sr0.56Ba0.44MnO3, revealing strong coupling between magnetic and electric orders and detailed spin excitation characteristics.

Contribution

It provides new insights into the coupling mechanisms between ferroelectric and magnetic orders in a multiferroic perovskite using neutron scattering techniques.

Findings

Ferroelectricity develops at 305 K with significant polarization.

Mn spins order below 200 K into a G-type magnetic structure.

Spin gap of approximately 4.6 meV and magnon peak at 43 meV observed.

Abstract

The magnetic order, spin dynamics, and crystal structure of the multiferroic Sr0.56Ba0.44MnO3 have been investigated using neutron and x-ray scattering. Ferroelectricity develops at TC=305 K with a polarization of 4.2 microC/cm2 associated with the displacements of the Mn ions, while the Mn4+ spins order below TN = 200 K into a simple G-type commensurate magnetic structure. Below TN the ferroelectric order decreases dramatically demonstrating that the two order parameters are strongly coupled. The ground state spin dynamics are characterized by a spin gap of 4.6(5) meV and the magnon density of states peaking at 43 meV. Detailed spin wave simulations with a gap and isotropic exchange of J=4.8(2) meV describe the excitation spectrum well. Above TN strong spin correlations coexist with robust ferroelectric order.