Trimer-based spin liquid candidate B a4NbI r3 O12

Ba4NbIr3O12, a material with a triangular planar geometry of Ir3O12 trimers, is described. Magnetic susceptibility measurements show it to be paramagnetic with no magnetic ordering down to 1.8 K despite the Curie-Weiss temperature (θCW) of -13 K. The material has a very low effective magnetic moment (μeff) of 0.80 μB/f.u. To look at the lower-temperature behavior, the specific heat (Cp) was measured down to 0.35 K; it shows no indication of magnetic ordering and fitting a power law to Cp vs T below 2 K yields the power α=3/4. Comparison to the trimer compound made with the 4d element Rh in place of the 5d element Ir, Ba4NbRh3O12, which is also paramagnetic (μeff=1.48μB/f.u., θCW=-23K), is presented. The analysis suggests that Ba4NbIr3O12 is a candidate spin liquid material.