Coexistence of Weak Ferromagnetism and Ferroelectricity in the High Pressure LiNbO3-type Phase of FeTiO3

TL;DR

This study demonstrates that high-pressure FeTiO3 adopts a LiNbO3-type structure exhibiting coexistence of ferroelectricity at room temperature and weak ferromagnetism below 120 K, validated by experimental and theoretical methods.

Contribution

It provides the first experimental evidence of coexistence of ferroelectricity and weak ferromagnetism in high-pressure FeTiO3, confirming symmetry-based design principles.

Findings

FeTiO3-II is ferroelectric at and below room temperature.

FeTiO3-II exhibits weak ferromagnetism below approximately 120 K.

The coexistence is explained by Dzyaloshinskii-Moriya interaction.

Abstract

We report the magnetic and electrical characteristics of a polycrystalline specimen of FeTiO3 synthesized at high pressure that is isostructural with acentric LiNbO3 (LBO). Piezoresponse force microscopy, optical second harmonic generation, and magnetometry demonstrate that FeTiO3-II is ferroelectric at and below room temperature and weakly ferromagnetic below ~120 K. These results validate symmetry-based materials design criteria and first principles calculations of coexistence between ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LBO structure. The high-pressure form of FeTiO3 stands out as a rare example of a ferroelectric exhibiting weak ferromagnetism generated by a Dzyaloshinskii-Moriya interaction.