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 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 10-fold 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, 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 an enhancement near 17 K in reported specific heat data.