Electronic charge transfer driven by spin cycloidal structure

TL;DR

This study demonstrates that in multiferroic RMn2O5 compounds, local electric displacements and ferroelectricity are driven by the spin-current mechanism, as evidenced by muon spin rotation and X-ray scattering experiments showing O ion spin polarization linked to Mn spin chirality.

Contribution

The paper provides experimental evidence that the spin-current mechanism causes charge transfer and ferroelectricity in multiferroic RMn2O5, highlighting the role of O ion spin polarization.

Findings

O ion spin polarization correlates with Mn spin chirality

Charge transfer driven by spin-current mechanism induces ferroelectricity

Muon and X-ray experiments confirm local electric displacements

Abstract

Muon spin rotation and resonant soft X-ray scattering experiments on prototype multiferroics RMn2O5 (R = Y, Sm) are used to demonstrate that the local electric displacements are driven by the spin-current (SC) mechanism. Small local electric displacements were evaluated by observing spin polarization at ligand O ions, for which implanted muons served as an extremely sensitive probe. Our results for YMn2O5 provide evidence that the spin polarization of O ions forming a spin cycloid chain with Mn spins increases in proportion to the vector spin chirality (Si x Sj ) of the Mn ions. This relationship strongly indicates that the charge transfer between O and Mn ions is driven by the SC mechanism, which leads to the ferroelectricity accompanying O spin polarization.