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 PrPd3S4 as well as magnetization and magnetic-susceptibility measurements of single-crystalline samples to examine the order parameter below TM=1.56 K. From the results of the inelastic-neutron-scattering and magnetization measurements, the ground state of the J-multiplet of Pr3+ under a cubic crystalline electric field with Th symmetry was determined to be the Γ4(2) triplet with the first excited state situated above 390 K. Since the dipolar operator and the Tα- and Tβ-type octupolar operators are proportional to the same matrix with the bases of the ground Γ4(2) triplet, the antiferromagnetic (AFM) alignment of the magnetic dipolar moments below TM 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. (author)