Tuning the multiferroic mechanisms of TbMnO3 by epitaxial strain

TL;DR

This study demonstrates that applying epitaxial strain to TbMnO3 significantly alters its magnetic and ferroelectric properties, enabling controlled tuning of multiferroic states for potential applications.

Contribution

It reveals how epitaxial strain switches the multiferroic mechanisms in TbMnO3, changing magnetic order and polarization direction, which was not previously demonstrated.

Findings

Magnetic order changes from incommensurate to commensurate under strain.

Ferroelectric polarization increases dramatically with strain.

Polarization direction shifts from c-axis to a-axis.

Abstract

A current challenge in the field of magnetoelectric multiferroics is to identify systems that allow a controlled tuning of states displaying distinct magnetoelectric responses. Here we show that the multiferroic ground state of the archetypal multiferroic TbMnO3 is dramatically modified by epitaxial strain. Neutron diffraction reveals that in highly strained films the magnetic order changes from the bulk-like incommensurate bc-cycloidal structure to commensurate magnetic order. Concomitant with the modification of the magnetic ground state, optical second-harmonic generation (SHG) and electric measurements show an enormous increase of the ferroelectric polarization, and a change in its direction from along the c- to the a-axis. Our results suggest that the drastic change of multiferroic properties results from a switch of the spin-current magnetoelectric coupling in bulk TbMnO3 to symmetric magnetostriction in epitaxially-strained TbMnO3. These findings experimentally demonstrate that epitaxial strain can be used to control single-phase spin-driven multiferroic states.