Epitaxial TbMnO3 thin films on SrTiO3 substrates: A structural study

TL;DR

This study investigates the structural evolution and domain microstructure of epitaxial TbMnO3 thin films on SrTiO3 substrates, revealing how film thickness influences symmetry, domain formation, and magnetic properties.

Contribution

It provides detailed insights into the structural transition, domain microstructure, and magnetic behavior of TbMnO3 thin films under strain, which was not previously characterized.

Findings

Thicker films evolve from tetragonal to orthorhombic structure.

High density of ferroelastic domains observed, as narrow as 4nm.

Induced ferromagnetism linked to domain wall density.

Abstract

TbMnO$_{3}$ films have been grown under compressive strain on (001)-oriented SrTiO$_{3}$ crystals. They have an orthorhombic structure and display the (001) orientation. With increasing thickness, the structure evolves from a more symmetric (tetragonal) to a less symmetric (bulk-like orthorhombic) structure, while keeping constant the in-plane compression thereby leaving the out-of-plane lattice spacing unchanged. The domain microstructure of the films is also revealed, showing an increasing number of orthorhombic domains as the thickness is decreased: we directly observe ferroelastic domains as narrow as 4nm. The high density of domain walls may explain the induced ferromagnetism observed in the films, while both the decreased anisotropy and the small size of the domains could account for the absence of a ferroelectric spin spiral phase.