Role of stacking defects on the magnetic behavior of CrCl₃

In the study of van der Waals-layered magnetic materials, the properties of CrCl₃ continue to attract attention. This compound is reported to undergo antiferromagnetic (AFM) ordering below ~14 K, with a ferromagneticlike region proposed to exist between 14 and 17 K. Ideally, the crystal structure is rhombohedral (R) below ~235 K, separated from a higher-temperature monoclinic (M) phase by a layer-sliding structural phase transition. However, the structural transition is often inhibited even in bulk single crystals, allowing M-type layer stacking, reported to have a tenfold greater interlayer magnetic coupling than R-type stacking, to be present at low temperature. To clarify the effect of stacking defects on CrCl₃, we report magnetization measurements on samples of varying crystalline quality. At low applied magnetic field, some crystals predominantly show the TN=14 K peak, but other crystals show hysteretic behavior and a magnetization enhancement at a slightly higher temperature (14 < T 17 K.) Samples with anomalous behavior exhibit a transition around ~2 T in isothermal magnetization-field data, providing evidence that M-type stacking defects are the source of these anomalies. Ground powder samples are especially likely to show strongly anomalous behavior. We suggest that the anomalous behavior arises from few-layer magnetic domains that form just above TN in an environment of mixed interlayer magnetic coupling strength. We argue that the influence of M-type stacking boundaries on sublattice magnetization is already observable in reported neutron scattering data, and may be responsible for a certain feature in reported specific heat data.