Subtle Structural Changes in LaFeO3 at High Pressure

Abstract

High-pressure neutron diffraction measurements of polycrystalline LaFeO3 are collected up to 5.5 and 6.4 GPa at 290 and 110 K, respectively. The bulk moduli are determined as B0(290 K) = 170(3) GPa and B0(110 K) = 175(1) GPa. The unit cell is found to compress anisotropically at both temperatures with the a-axis compressing preferentially. A crossover in lattice parameters is observed, from a > c to c > a, at 2 GPa at 290 K and at 1.7 GPa at 110 K. The magnetic moment remains unchanged over the pressure range investigated, with a value of 4.4 μB and 4 μB at 110 and 290 K, respectively. Analysis of the octahedral tilting angles and the spontaneous lattice strains shows an increased orthorhombic distortion with pressure, but shows no trend toward a change in symmetry. High-pressure Raman spectroscopy measurements at room temperature are in agreement with the diffraction data.