Phase transitions of the ferroelectric ${({\mathrm{ND}}_{4})}_{2}{\mathrm{FeCl}}_{5}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{D}}_{2}\mathrm{O}$ under magnetic field

Letter

Phase transitions of the ferroelectric ${({ND}_{4})}_{2} {FeCl}_{5} \cdot D_{2} O$ under magnetic field

Shaozhi Li and Randy S. Fishman

Phys. Rev. B 104, L060407 – Published 17 August 2021

Abstract

Due to the strong coupling between magnetism and ferroelectricity, ${({ND}_{4})}_{2} {FeCl}_{5} \cdot D_{2} O$ exhibits several intriguing magnetic and electric phases. In this Letter, we include higher-order onsite anisotropic spin interactions to explain the ferroelectric phase transitions of ${({ND}_{4})}_{2} {FeCl}_{5} \cdot D_{2} O$ in a magnetic field and to produce the large weights of high-order harmonic components in the cycloid structure that are observed from neutron diffraction experiments. Moreover, we predict a new ferroelectric phase sandwiched between the FE II and FE III phases in a magnetic field. By emphasizing the importance of the higher-order spin anisotropic interactions, our work provides a framework to understand multiferroic materials with rich phase diagrams.