2017/01/19 by J. P. Sheckelton, K. W. Plumb, B. A. Trump +2 · 1 citation
Physics and Astronomy · #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1039/c6qi00470a
23 pages, 9 figures, 4 tables in Inorg. Chem. Front., 2017
arxiv created 2017/01/19 · arxiv updated 2017/01/20
Insulating Nb3Cl8 is a layered chloride consisting of two-dimensional triangular layers of Seff = 1/2 Nb3Cl13 clusters at room temperature. Magnetic susceptibility measurement show a sharp, hysteretic drop to a temperature independent value below T = 90 K. Specific heat measurements show that the transition is first order, with ΔS ≈ 5 \mathrmJ ⋅ K-1 ⋅ mol f.u.-1, and a low temperature T-linear contribution originating from defect spins. Neutron and X-ray diffraction show a lowering of symmetry from trigonal P3m1 to monoclinic C2/m symmetry, with a change in layer stacking from -AB-AB- to -AB^′-BC^′-CA^′- and no observed magnetic order. This lowering of symmetry and rearrangement of successive layers evades geometric magnetic frustration to form a singlet ground state. It is the lowest temperature at which a change in stacking sequence is known to occur in a Van-der-Waals solid, occurs in the absence of orbital degeneracies, and suggests that designer 2-D heterostructures may be able to undergo similar phase transitions.