Synthesis of a d2 kagome lattice antiferromagnet, (CH3NH3)2NaV3F12

Abstract

The ground-state of S = 1 kagome lattice antiferromagnets (KLAFs), in the presence of strong geometric frustration and the smallest integer spin, has the potential to host a range of non-trivial magnetic phases including a quantum spin liquid. The effect of local geometry and metal-ion electronic structure on the formation of these predicted phases remain unknown due to, in part, the lack of an ideal analyte. Herein, a kagome lattice compound, (CH₃NH₃)₂NaV₃F₁₂ (1-V), featuring a single distinct V³⁺ (d²) site in the Rm space group, was synthesized hydrothermally. In this S = 1, d² system, the trivalent vanadium ions are tetragonally compressed due to Jahn–Teller distortion. The interlayer methylammonium cations show static positional disorder with three possible orientations. The negative Curie–Weiss temperature and dominant antiferromagnetic interactions make 1-V a candidate to study S = 1 KLAF physics. The frequency-dependence of ac magnetic susceptibility and the heat capacity results suggest that 1-V has a spin glass ground state. This freezing of the spin dynamics may be due to competing exchange interactions, structural imperfection arising from the static disorder of the interlayer methylammonium cations or the presence of ‘defect’-like spins.