Ferroelectricity and ferromagnetism in EuTiO3 nanowires

TL;DR

This study predicts that EuTiO3 nanowires can exhibit multiferroic properties, including ferroelectricity and ferromagnetism, induced by nanoscale effects and surface stress, with potential applications in multifunctional devices.

Contribution

The paper introduces a theoretical prediction of multiferroic behavior in EuTiO3 nanowires, highlighting size-dependent ferroelectric and ferromagnetic phase induction.

Findings

Ferroelectric polarization induced in nanowires due to surface stress.

Ferromagnetic phase emerges at low temperatures in nanowires.

Multiferroic properties are size and temperature dependent.

Abstract

We predicted the ferroelectric-ferromagnetic multiferroic properties of EuTiO3 nanowires and generated the phase diagrams in coordinates of temperature and wire radii. The calculations were performed within the Landau-Ginzburg-Devonshire theory with phenomenological parameters extracted from tabulated experimental data and first principles calculations. Since bulk EuTiO3 is antiferromagnetic at temperatures lower than 5.5 K and paraelectric at all temperatures, our goal was to investigate the possibility of inducing the ferroelectric and ferromagnetic properties of EuTiO3 by reducing the bulk to nanosystems. Our results indicate that ferroelectric spontaneous polarization of ~0.1-0.5C/m2 is induced in EuTiO3 nanowires due to the intrinsic surface stress, which is inversely proportional to the nanowire radius. The spontaneous polarization exists at temperatures lower than 300 K, for the wire radius less than 1 nm and typical surface stress coefficients ~ 15 N/m. Due to the strong biquadratic magnetoelectric coupling, the spontaneous polarization in turn induces the ferromagnetic phase at temperatures lower than 30 K for 2 nm nanowire, and at temperatures lower than 10 K for 4 nm nanowire in EuTiO3. Thus we predicted that the EuTiO3 nanowires can be the new ferroelectric-ferromagnetic multiferroic.