Abstract
The magnetic order, spin dynamics, and crystal structure of the multiferroic have been investigated using neutron and x-ray scattering. Ferroelectricity develops at K with a polarization of 4.2 associated with the displacements of the Mn ions, while the spins order below K into a simple -type commensurate magnetic structure. Below the ferroelectric order decreases dramatically, demonstrating that the two order parameters are strongly coupled. The ground state spin dynamics is 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 meV describe the excitation spectrum well. Above strong spin correlations coexist with robust ferroelectric order.
- Received 12 June 2014
- Revised 19 September 2014
DOI:https://doi.org/10.1103/PhysRevB.90.140401
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