Origin of ferroelectricity in high-$T_c$ magnetic ferroelectric CuO

TL;DR

This paper elucidates the mechanism behind the high transition temperature of multiferroicity in CuO, revealing the roles of magnetic sublattices and weak spin frustration through combined computational models.

Contribution

It provides a detailed explanation of high-Tc multiferroicity in CuO using first-principles calculations and an effective Hamiltonian model, highlighting the importance of magnetic sublattices and spin frustration.

Findings

CuO has two magnetic sublattices with strong intrasublattice interactions.

Weak intersublattice interactions cause incommensurate spin excitations.

Spin frustration enhances entropy, stabilizing the multiferroic phase.

Abstract

Cupric oxide is a unique magnetic ferroelectric material with a transition temperature significantly higher than the boiling point of liquid nitrogen. However, the mechanism of high-T$_c$ multiferroicity in CuO remains puzzling. In this paper, we clarify the mechanism of high-T$_c$ multiferroicity in CuO, using combined first-principles calculations and an effective Hamiltonian model. We find that CuO contains two magnetic sublattices, with strong intrasublattice interactions and weakly frustrated intersublattice interactions, which may represent one of the main reasons for the high ordering temperature of the compound. The weak spin frustration leads to incommensurate spin excitations that dramatically enhance the entropy of the mutliferroic phase and eventually stabilize that phase in CuO.