Magnetostructural Coupling at the N\'eel point in YNiO3 Single Crystals

TL;DR

This study reveals strong magnetostrictive effects at the Ne9el point in YNiO3 single crystals, indicating significant spin-lattice coupling and supporting the existence of magnetism-driven ferroelectricity in RNiO3 perovskites.

Contribution

It provides experimental evidence of magnetostriction and lattice anomalies at TN in YNiO3, highlighting the role of symmetric superexchange in magnetoelastic coupling.

Findings

Pronounced lattice contraction along the b axis below TN

Strong spin-lattice coupling consistent with theoretical predictions

Support for magnetism-driven ferroelectricity in RNiO3 family

Abstract

The recent discovery of superconductivity in infinite layer thin films and bulk Ruddlesden-Popper nickelates has stimulated the investigation of other predicted properties of these materials. Among them, the existence of magnetism-driven ferroelectricity in the parent compounds RNiO3 (R = 4f lanthanide and Y) at the onset of the N\'eel order, TN, has remained particularly elusive. Using diffraction techniques, we reveal here the existence of magnetostriction at TN in bulk YNiO3 single crystals. Interestingly, the associated lattice anomalies are much more pronounced along the b crystal axis, which coincides with the electric polarization direction expected from symmetry arguments. This axis undergoes an abrupt contraction below TN that reaches deltab/b ~ - 0.01 %, a value comparable to those found in some magnetoresistive manganites and much larger than those reported for magnetism-driven multiferroics. This observation suggests a strong spin-lattice coupling in these materials, consistent with theoretical predictions. Using the symmetry-adapted distortion mode formalism we identify the main ionic displacements contributing to the lattice anomalies and discuss the most likely polar displacements below TN. Furthermore, our data support symmetric superexchange as the most likely mechanism responsible for the magnetoelastic coupling. These results, that may be common to the full RNiO3 family, provide new experimental evidence supporting the predicted existence of magnetism-driven ferroelectricity in RNiO3 perovskites