Doping effects on trimerization and magnetoelectric coupling of single crystal multiferroic (Y,Lu)MnO3

TL;DR

This study investigates how doping affects the structural and dielectric properties of multiferroic (Y,Lu)MnO3 crystals, revealing complex doping-dependent behaviors and insights into the spin-lattice coupling mechanisms.

Contribution

It provides new experimental data on doping effects in hexagonal RMnO3, highlighting the doping-dependent anomalies and advancing understanding of spin-lattice interactions.

Findings

Doping causes progressive changes in physical properties.

Anomalies at the Néel temperature are observed across all doping levels.

Unusual doping dependence of the anomalies suggests complex spin-lattice coupling.

Abstract

Hexagonal RMnO3 is a multiferroic compound with a giant spin-lattice coupling at an antiferromagnetic transition temperature [1]. Despite extensive studies over the past two decades, however, the origin and underlying microscopic mechanism of the strong spin-lattice coupling remain still very much elusive. In this study, we have tried to address this problem by measuring the thermal expansion and dielectric constant of doped single crystals Y1-xLuxMnO3 with x = 0, 0.25, 0.5, 0.75, and 1.0. From these measurements, we confirm that there is a progressive change in the physical properties with doping. At the same time, all our samples exhibit clear anomalies at TN, even in the samples with x = 0.5 and 0.75 as opposed to some earlier ideas, which suggests an unusual doping dependence of the anomaly. Our work reveals yet another interesting facet of the spin lattice coupling issue in hexagonal RMnO3.