Doping dependence of spin-lattice coupling and two-dimensional ordering in multiferroic hexagonalY1−xLuxMnO3(0≤x≤1)

Abstract

We have examined a complete phase diagram of ${\text{Y}}_{1\ensuremath{-}x}{\text{Lu}}_{x}{\text{MnO}}_{3}$ with $0\ensuremath{\le}x\ensuremath{\le}1$ by using bulk measurements and neutron-diffraction studies. With increasing Lu concentration, Curie-Weiss temperature and Neel temperature are found to increase continuously while the two-dimensional nature of short-range magnetic correlation persists even in the paramagnetic phase throughout the entire doping range. At the same time, the lattice constants and the unit-cell volume get contracted with Lu doping, i.e., chemical pressure effect. This decrease in the lattice constants and the unit-cell volume then leads naturally to an increased magnetic exchange interaction as found in our local spin-density approximation band calculations. We also discover that there is strong correlation in the temperature dependence of a volume anomaly at ${T}_{N}$ and the magnetic moments.