Crystal Growth, Exfoliation and Magnetic Properties of Quaternary Quasi-Two-Dimensional CuCrP$_2$S$_6$

TL;DR

This study reports the synthesis, structural characterization, exfoliation, and magnetic properties of CuCrP$_2$S$_6$, a quasi-2D compound related to 2D magnets, revealing antiferromagnetic order and structural transitions.

Contribution

It presents optimized growth conditions, structural and compositional analysis, exfoliation down to few layers, and magnetic property measurements of CuCrP$_2$S$_6$, a novel quasi-2D magnetic material.

Findings

Crystals exhibit layered morphology and can be exfoliated to 2.8 nm thickness.

CuCrP$_2$S$_6$ shows antiferromagnetic order below 30 K.

Structural changes and antiferroelectric anomalies observed at 140-200 K.

Abstract

We report optimized crystal growth conditions for the quaternary compound CuCrP$_2$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. CuCrP$_2$S$_6$ is structurally closely related to the $M_2$P$_2$S$_6$ family ($M$: transition metal), which contains several compounds that are under investigation as 2D magnets. As-grown crystals exhibit a plate-like, layered morphology as well as a hexagonal habitus. We present successful exfoliation of such as-grown crystals down to thicknesses of 2.8 nm corresponding to 4 layers. CuCrP$_2$S$_6$ crystallizes in the monoclinic space group $C2/c$. Magnetization measurements reveal an antiferromagnetic ground state with $T_\textrm{N} \approx 30$ 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.