Multiferroic properties of uniaxially compressed orthorhombic HoMnO3 thin films

TL;DR

This study investigates how uniaxial compressive strain along the a-axis alters the multiferroic properties of orthorhombic HoMnO3 thin films, revealing significant differences from bulk behavior in ferroelectric and magnetic transitions.

Contribution

It demonstrates the effect of epitaxial uniaxial strain on multiferroic properties of HoMnO3 thin films using a specific substrate to isolate strain effects.

Findings

Strained films become ferroelectric at higher temperatures (37.5 K) than relaxed films (25 K).

Strained films show a different magnetic order wave vector (~0.49) compared to relaxed films (~0.41).

Strain significantly modifies the multiferroic transition temperatures and magnetic ordering.

Abstract

Multiferroic properties of orthorhombic HoMnO3 (Pbnm space group) are significantly modified by epitaxial compressive strain along the a-axis. We are able to focus on the effect of strain solely along the a-axis by using an YAlO3 (010) substrate, which has only a small lattice mismatch with HoMnO3 along the other in-plane direction (the c-axis). Multiferroic properties of strained and relaxed HoMnO3 thin films are compared with those reported for bulk, and are found to differ widely. A relaxed film exhibits bulk-like properties such as a ferroelectric transition temperature of 25 K and an incommensurate antiferromagnetic order below 39 K, with an ordering wave vector of (0 qb 0) with qb ~ 0.41 at 10 K. A strained film becomes ferroelectric already at 37.5 K and has an incommensurate magnetic order with qb ~ 0.49 at 10 K.