Multiferroic properties of epitaxially stabilized hexagonal DyMnO3 thin films

TL;DR

This study reports the fabrication and characterization of epitaxial hexagonal DyMnO3 thin films, revealing ferroelectric and antiferromagnetic properties with enhanced polarization and complex magnetic behavior due to geometric frustration.

Contribution

First demonstration of epitaxial stabilization of hexagonal DyMnO3 thin films exhibiting multiferroic properties distinct from bulk forms.

Findings

Ferroelectricity observed below 70 K with enhanced polarization.

Antiferromagnetic Neel temperature around 60 K.

Hysteresis in magnetization suggesting spin glass behavior.

Abstract

We fabricated epitaxial thin films of hexagonal DyMnO3, which otherwise form in a bulk perovskite structure, via deposition on Pt(111)//Al2O3 (0001) and YSZ(111) substrates: each of which has in-plane hexagonal symmetry. The polarization hysteresis loop demonstrated the existence of ferroelectricity in our hexagonal DyMnO3 films at least below 70 K. The observed 2.2 uC/cm^2 remnant polarization at 25 K corresponded to a polarization enhancement by a factor of 10 compared to that of the bulk orthorhombic DyMnO3. Interestingly, this system showed an antiferroelectric-like feature in its hysteresis loop. Our hexagonal DyMnO3 films showed an antiferromagnetic Neel temperature around 60 K and a spin reorientation transition around 40 K. We also found a clear hysteresis in the temperature dependence of the magnetization, which was measured after zero-field-cooling and field-cooling. This hysteresis may well have been of spin glass origin, which was likely to arise from the geometric frustration of antiferromagnetically-coupled Mn spins with an edge-sharing triangular lattice.