Crystal growth, magnetic, and magnetocaloric properties of J_eff = 1/2 quantum antiferromagnet CeCl_3

Abstract

We report growth of high-quality single crystals of CeCl3 using a modified Bridgman Stockbarger method in an infrared image furnace. The grown crystals are characterized using single-crystal/powder X-ray diffraction, Laue X-ray diffraction, Raman spectroscopy, magnetization, and heat capacity probes. CeCl3 crystallizes in a hexagonal structure with a weak trigonal distortion. The Raman spectrum at 300 K showcases five, clearly resolvable, phonon modes at 106.8, 181.2, 189, 213, and 219.7 wavenumbers. The magnetic susceptibility show a large anisotropy with a broad peak in the perpendicular orientation, which is explained using the crystal field theory. The crystal field in CeCl3 splits the J = 5/2 manifold of Ce3+ into three Kramers doublets, resulting in a well-isolated ground state. In the specific heat, no magnetic ordering is detected above 2 K. However, in non-zero fields the low-temperature specific heat changes dramatically, showcasing a peak at 2.5 K under a moderate field of 30 kOe. The weak Ce-Ce exchange, large Ce moment in the crystal field ground state, and significant anisotropy are ingredients for realizing a high magnetocaloric effect. A maximum entropy change of 23 J/Kg/K is observed near 2.5 K in fields ranging from 50 kOe to 60 kOe. These values are comparable to some of the best Gd-based magnetocaloric materials, signifying the potential of CeCl3 as a magnetic coolant.