Crystal growth, exfoliation, and magnetic properties of quaternary quasi-two-dimensional CuCrP2S6

Abstract

We report optimized crystal growth conditions for the quaternary compound ${\mathrm{CuCrP}}_{2}{\mathrm{S}}_{6}$ by chemical vapor transport. Compositional and structural characterization of the obtained crystals were carried out by means of energy-dispersive x-ray spectroscopy and powder x-ray diffraction. ${\mathrm{CuCrP}}_{2}{\mathrm{S}}_{6}$ is structurally closely related to the ${M}_{2}{\mathrm{P}}_{2}{\mathrm{S}}_{6}$ family ($M$: transition metal), which contains several compounds that are under investigation as 2D magnets. As-grown crystals exhibit a platelike, layered morphology as well as a hexagonal habitus. We present successful exfoliation of such as-grown crystals down to thicknesses of 2.6 nm corresponding to four layers. ${\mathrm{CuCrP}}_{2}{\mathrm{S}}_{6}$ crystallizes in the monoclinic space group $C2/c$. Magnetization measurements reveal an antiferromagnetic ground state with ${T}_{\text{N}}\ensuremath{\approx}30$ K and a positive Curie-Weiss temperature in agreement with dominant ferromagnetic intralayer coupling. Specific heat measurements confirm this magnetic phase transition and the magnetic order is suppressed in an external magnetic field of about 6 T (8 T) applied parallel (perpendicular) to the $ab$ plane. At higher temperatures between 140--200 K, additional broad anomalies associated with structural changes accompanying antiferroelectric ordering are detected in our specific heat studies.