Ferroelectricity induced by acentric spin-density waves in YMn$_2$O$_5$

TL;DR

This paper demonstrates that acentric spin-density waves in YMn₂O₅ induce ferroelectricity, with a model predicting polarization from magnetic structure that matches temperature-dependent experimental data.

Contribution

It introduces a magneto-elastic coupling model linking magnetic structures to ferroelectric polarization in YMn₂O₅, explaining polarization behavior across phase transitions.

Findings

Magnetic structures are spin-density waves without a global center of symmetry.

The model accurately predicts the temperature dependence of polarization.

Reproduces the sign reversal of polarization at phase transition.

Abstract

The commensurate and incommensurate magnetic structures of the magnetoelectric system YMn$_{2}$O$_{5}$, as determined from neutron diffraction, were found to be spin-density waves lacking a global center of symmetry. We propose a model, based on a simple magneto-elastic coupling to the lattice, which enables us to predict the polarization based entirely on the observed magnetic structure. Our data accurately reproduce the temperature-dependence of the spontaneous polarization, in particular its sign reversal at the commensurate-incommensurate transition.