Four-spin ring interaction as a source of unconventional magnetic orders in orthorhombic perovskite manganites

TL;DR

This study combines ab initio calculations and Monte Carlo simulations to reveal that four-spin ring exchange interactions induce exotic magnetic orders in orthorhombic perovskite manganites, explaining experimental inconsistencies.

Contribution

It identifies four-spin ring exchange as a key factor in stabilizing unconventional magnetic orders in o-$R$MnO$_3$, providing new insights into their magnetic and ferroelectric properties.

Findings

Stabilization of exotic magnetic orders such as w-spiral, H-AFM, and I-AFM.

Resolution of experimental contradictions in magnetic and ferroelectric measurements.

Demonstration of the role of four-spin ring exchange interactions in magnetic order formation.

Abstract

We use ab initio electronic structure calculations in combination with Monte Carlo simulations to investigate the magnetic and ferroelectric properties of bulk orthorhombic HoMnO$_3$ and ErMnO$_3$. Our goals are to explain the inconsistencies in the measured magnetic properties of the orthorhombic perovskite manganites (o-$R$MnO$_3$) with small rare-earth ($R$) cations or Y, as well as the contradictions between the directions and amplitudes of the electric polarizations reported by different experimental groups. Our computations stabilize several exotic magnetic orders (so-called w-spiral, H-AFM and I-AFM), whose presence resolve the contradictions in the measured magnetic and ferroelectric properties of o-$R$MnO$_3$. We show that these orders emerge due to strong four-spin ring exchange interactions.