Relationship between crystal structure and multiferroic orders in orthorhombic perovskite manganites

TL;DR

This study investigates how structural variations in orthorhombic perovskite manganites influence their multiferroic magnetic and electric properties, using experimental and computational methods to understand strain effects.

Contribution

It provides new insights into how chemical pressure and epitaxial strain differently affect lattice parameters and magnetic order in o-$R$MnO$_3$, linking structure to multiferroic behavior.

Findings

Chemical pressure and strain alter lattice parameters differently.

Structural variations impact magnetic exchange interactions.

Magnetic differences influence electric polarization.

Abstract

We use resonant and non-resonant X-ray diffraction measurements in combination with first-principles electronic structure calculations and Monte Carlo simulations to study the relationship between crystal structure and multiferroic orders in the orthorhombic perovskite manganites, o-$R$MnO$_3$ ($R$ is a rare-earth cation or Y). In particular, we focus on how the internal lattice parameters (Mn-O bond lengths and Mn-O-Mn bond angles) evolve under chemical pressure and epitaxial strain, and the effect of these structural variations on the microscopic exchange interactions and long-range magnetic order. We show that chemical pressure and epitaxial strain are accommodated differently by the crystal lattice of o-$R$MnO$_3$, which is key for understanding the difference in magnetic properties between bulk samples and strained films. Finally, we discuss the effects of these differences in the magnetism on the electric polarization in o-$R$MnO$_3$.