DOI: 10.1098/rsta.2022.0332 ISSN:
A structural study of PrCrO
3
under extreme conditions: a comparison with the effects of doping
C. L. Bull, N. P. Funnell, C. J. Ridley
The nuclear and magnetic structure of
PrCrO
3
has been investigated using neutron and X-ray powder diffraction as a function of pressure and temperature. The orthorhombic symmetry (space group
P
b
n
m
) remains stable up to the highest temperature (1500 K) and pressure (approx.
6
GPa
) considered. There is a crossover in the magnitude of the
a-
and
b
-lattice parameters at approximately 1135 K, caused by competing effects of octahedral tilting and distortion. The material is antiferromagnetic (
T
N
≈
240
K) with
P
b
′
n
′
m
symmetry, with a maximum moment of
2.34
(
2
)
μ
b
on the
Cr
3
+
sites aligned along the direction of the
a
-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
PrCrO
3
are compared extensively in the wider context of other lanthanide orthochromites, and the comparative effects of
A
- and
B
-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 materials (Part 1)’.