A New Multipolar Ordering Compound, Rare-Earth Palladium Bronze PrPd3S4

Specific heat and magnetization measurements were performed on single crystalline PrPd₃S₄. A λ-type anomaly at T_M = 1.56 K in the specific heat shifts to higher temperatures by magnetic fields, begins to shift to lower temperatures above 2 T, and disappears above 3.6 T. The 4f ground state of Pr³⁺ was deduced to be a magnetic triplet. Below T_M, the magnetic susceptibility increases while no spontaneous magnetization appears. These results strongly reveal that PrPd₃S₄ shows a multipolar ordering at T_M. The most probable ordering state for PrPd₃S₄ is an antiferroquadrupolar (AFQ) ordering since the B-T phase diagrams are of the “re-entrant” type, which is typical for AFQ ordering compounds.