Supplementary material from "A structural study of PrCrO₃ under extreme conditions: a comparison with the effects of doping" release_ssjnjy4aybgkfeuvmrf5od7dqe

Abstract

The nuclear and magnetic structures of PrCrO₃ have been investigated using neutron and X-ray powder diffraction as a function of pressure and temperature. The orthorhombic symmetry (space group <i>Pbnm</i>) remains stable up to the highest temperature (1500 K) and pressure (approx. 6 GPa) considered. There is a crossover in the magnitude of the <i>a</i> and <i>b</i>-lattice parameters at approximately 1135 K, caused by competing effects of octahedral tilting and distortion. The material is antiferromagnetic (<i>T</i>_N ≈ 240 K) with <i>Pb</i>'<i>n</i>'<i>m</i> symmetry, with a maximum moment of 2.34(2) μ_<i>b</i> on the Cr³⁺ sites aligned along the direction of the <i>a</i>-axis. The application of pressure shows an abnormal softening in the unit-cell volume, which is suggestive of a continuous approach to a second-order phase transition. Raman spectroscopy measurements at ambient temperature were collected as a function of pressure up to approximately 12 GPa, with discontinuous mode-behaviour further suggesting the existence of a transition above 7 GPa. The measured structural-changes in PrCrO₃ are compared extensively in the wider context of other lanthanide orthochromites, and the comparative effects of <i>A</i>- and <i>B</i>-site substitution on the polyhedral tilts and distortion are discussed.This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging, modern materials (Part 1)'.
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