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

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.

arXiv comment8 pages, 4 figures

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• Hexagonal Sr0.6Ba0.4MnO3: Spin and Dipole Coupling via Local Structure
• Magnetic and ferroelectric properties of Sr${}_{1-x}$Ba${}_x$MnO${}_3$ from first principles
• Local atomic and magnetic structure of multiferroic (Sr,Ba)(Mn,Ti)O${}_3$
• Local structures and local exchange interactions in doped magnetic materials of different dimensionality