Frustrated magnetic state of Mott Insulating TiF₃

We present magnetic susceptibility, optical, and heat capacitance measurements of perovskite TiF₃. We find that the optical response favors an insulating state with a local moment magnetic response consistent with an S = 1/2 local moment per Ti⁺³ ion. Analysis of the magnetism gives an antiferromagnetic exchange coupling with a net Weiss temperature of order 25 K. However, the system shows no susceptibility peak at this temperature scale and appears free of long-range antiferromagnetic order down to 3 K, thus promoting the status of this simple, nearly cubic perovskite structured material to a candidate spin liquid.