Origin of ferroelectricity in high $T_c$ magnetic ferroelectric CuO

TL;DR

This paper investigates the high-temperature ferroelectricity in CuO, revealing that its weak spin frustration and unique magnetic structure contribute to its elevated ordering temperature, offering insights for discovering new high-$T_c$ multiferroics.

Contribution

It demonstrates that CuO's high $T_c$ ferroelectricity arises from its nearly commensurate spiral magnetic structure stabilized by Dzyaloshinskii-Moriya interaction, suggesting a pathway for finding similar materials.

Findings

CuO has a high ordering temperature (~230K) due to weak spin frustration.

The magnetic structure of CuO is nearly commensurate and stabilized by Dzyaloshinskii-Moriya interaction.

Weak spin frustration is key to high $T_c$ in magnetic ferroelectrics.

Abstract

"Magnetic ferroelectric" has been found in a wide range of spiral magnets. However, these materials all suffer from low critical temperatures, which are usually below 40 K, due to strong spin frustration. Recently, CuO has been found to be multiferroic at much higher ordering temperature ($\sim$ 230K). To clarify the origin of the high ordering temperature in CuO, we investigate the structural, electronic and magnetic properties of CuO via first-principles methods. We find that CuO has very special nearly commensurate spiral magnetic structure, which is stabilized via the Dzyaloshinskii-Moriya interaction. The spin frustration in CuO is relatively weak, which is one of the main reasons that the compound have high ordering temperature. We propose that high $T_c$ magnetic ferroelectric materials can be found in double sublattices of magnetic structures similar to that of CuO.