Multiferroic CuCrO2 under high pressure: <i>In situ</i> X-ray diffraction and Raman spectroscopic studies

Abstract

The compression behavior of delafossite compound CuCrO2 has been investigated by in situ x-ray diffraction (XRD) and Raman spectroscopic measurements up to 23.2 and 34 GPa, respectively. X-ray diffraction data show the stability of ambient rhombohedral structure up to ∼23 GPa. Material shows large anisotropy in axial compression with c-axis compressibility, κc = 1.26 × 10−3(1) GPa−1 and a-axis compressibility, κa = 8.90 × 10−3(6) GPa−1. Our XRD data show an irreversible broadening of diffraction peaks. Pressure volume data when fitted to 3rd order Birch-Murnaghan equation of state give the value of bulk modulus, B0 = 156.7(2.8) GPa with its pressure derivative, B0′ as 5.3(0.5). All the observed vibrational modes in Raman measurements show hardening with pressure. Appearance of a new mode at ∼24 GPa indicates the structural phase transition in the compound. Our XRD and Raman results indicate that CuCrO2 may be transforming to an ordered rocksalt type structure under compression.