Neutron scattering studies of the quasi-2D antiferromagnet CrCl₃

The magnetic behavior of quasi-two-dimensional materials is a frontier of materials research, of interest both for potential applications and to better understand the behavior of 2D systems. One such material is CrCl₃, which exhibits at least two magnetic transitions on cooling [1]. Below 17 K, an intermediate region with ferromagnetic (FM) behavior is reached, thought to have FM intralayer order but interlayer disorder. Below ~14 K, antiferromagnetic (AFM) interlayer ordering is observed. Applied magnetic field can drive the AFM order into an FM-like state. To elucidate structural and magnetic behavior, we performed neutron scattering experiments on CrCl₃. Single crystal neutron scattering in the AFM phase revealed, in addition to AFM Bragg peaks, diffuse scattering along the out-of-plane direction. Out-of-plane magnetic field resulted in changes to AFM Bragg peak intensities that appear inconsistent with a simple coherent spin rotation picture, as well as a slower suppression of diffuse scattering than of the peak intensities. For both ground powder and a single crystal, an anomalous increase in the in-plane lattice constant was observed below ~50 K.

[1] McGuire, et al. Phys. Rev. Mater. 1 014001 (2017).