Antiferromagnetic Alignment of Magnetic Dipolar Moments Observed by Neutron Powder Diffraction in Rare-Earth Palladium Bronze PrPd3S4

Neutron powder diffraction and inelastic-neutron-scattering experiments have been performed on PrPd 3 S 4 as well as magnetization and magnetic-susceptibility measurements of single-crystalline samples to examine the order parameter below T M = 1.56 K. From the results of the inelastic-neutron-scattering and magnetization measurements, the ground state of the J -multiplet of Pr 3+ under a cubic crystalline electric field with T h symmetry was determined to be the Γ 4 (2) triplet with the first excited state situated above 390 K. Since the dipolar operator and the T α - and T β -type octupolar operators are proportional to the same matrix with the bases of the ground Γ 4 (2) triplet, the antiferromagnetic (AFM) alignment of the magnetic dipolar moments below T M observed in the neutron powder diffraction experiment implies two possible ordering states, i.e., AFM ordering induced by a dipolar interaction and antiferro-octupolar ordering induced by an octupolar interaction.