Magnetic behavior and spin-lattice coupling in cleavable van der Waals layered CrCl3 crystals

Abstract

CrCl3 is a layered insulator that undergoes a crystallographic phase transition below room temperature and orders antiferromagnetically at low temperature. Weak van der Waals bonding between the layers and ferromagnetic in-plane magnetic order make it a promising material for obtaining atomically thin magnets and creating van der Waals heterostructures. In this work we have grown crystals of CrCl3, revisited the structural and thermodynamic properties of the bulk material, and explored mechanical exfoliation of the crystals. We find two distinct anomalies in the heat capacity at 14 and 17 K confirming that the magnetic order develops in two stages on cooling, with ferromagnetic correlations forming before long range antiferromagnetic order develops between them. This scenario is supported by magnetization data. A magnetic phase diagram is constructed from the heat capacity and magnetization results. We also find an anomaly in the magnetic susceptibility at the crystallographic phase transition, indicating some coupling between the magnetism and the lattice. First principles calculations accounting for van der Waals interactions also indicate spin-lattice coupling, and find multiple nearly degenerate crystallographic and magnetic structures consistent with the experimental observations. Finally, we demonstrate that monolayer and few-layer CrCl3 specimens can be produced from the bulk crystals by exfoliation, providing a path for the study of heterostructures and magnetism in ultrathin crystals down to the monolayer limit.

Valley polarization in monolayer CrX2 (X = S, Se) with magnetically doping and proximity coupling

“…Such tiny mismatches are well desirable for experimental explorations. Moreover, bulk CrCl 3 has been successfully exfoliated down to the monolayer limit [60,61], offering the possibility for creating van der Waals heterostructures.…”

Physical properties and thermal stability of Fe5−xGeTe2 single crystals

“…Several types of symmetry changes could be associated with such a stacking transition, including the shift to a monoclinic cell as in vdW CrI 3 and CrCl 3 . 20,21 In those systems, the main effect is a change in layer spacing with a larger layer spacing observed in the monoclinic phases that are the high T states. Other types of stacking-related transitions are also possible, such as transitioning to one layer per unit cell or from the rhombohedral ABC stacking to a primitive AAA stacking.…”

Super-exchange theory for polyvalent anion magnets

“…The electronic state of cation is of great significance to analyze the magnetic ordering. In the traditional class of magnetic materials, every anion possesses equivalent valence state, like CrCl 3 [17](−1 for Cl − ). As a consequence, the electronic state (3d 3 for Cr 3+ ) of cations in all super-exchange paths (i.e.…”