Griffiths phase in antiferromagnetic CuCr0.95Ti0.05O2

Abstract

Delafossite compound, CuCrO2, popularly known as transparent conducting oxide, has previously been reported to demonstrate antiferromagnetic ordering of the triangular magnetic lattice below 24 K. We find that mere 5% Ti-substitution at Cr-site, leads to short range magnetic correlations, manifested as non-analytical behaviour of H/M and other anomalies in the low magnetic field dc magnetization, ac magnetic susceptibility, time dependent magnetization, and isothermal remanent magnetization. The ac susceptibility measured at different applied frequencies do not show any frequency dependence, ruling out the glassy magnetic phase. The short-range magnetic correlations are observed over a wide temperature range starting from 180 K and below, until the system orders antiferromagnetically at 22 K. These correlations which are most pronounced at low values of applied magnetic field, get readily suppressed when the fields exceed 0.5 T. Signatures associated with these short-range correlations seem to fit a Griffiths-like phase description. The results of heat capacity measurement with and without magnetic field, provides additional information about the dimensionality of the magnetic interactions. Rietveld refinement of the X-ray diffraction data reveals that the highly anisotropic crystal structure remains unaffected with the substitution. A static disorder driven magnetic inhomogeneity arising in the triangular magnetic sublattice of Cr ions decreases the dimensionality of magnetic interactions, and seems to be the possible origin of this interesting magnetic behaviour.