Pressure-Induced Antiferromagnetic Order in Filled Skutterudite PrFe₄P₁₂ Studied by Single-Crystal High-Pressure Neutron Diffraction

Abstract

The order parameter in the pressure-induced insulating phase of the filled skutterudite compound PrFe 4 P 12 has been investigated using a high-pressure single-crystal neutron diffraction technique. Clear evidence of the antiferromagnetic order with the propagation vector q = (1, 0, 0) was observed in the insulating phase above 2.7 GPa. The q = (1, 0, 0) structure is identical with that in the nonmagnetic ordered phase below 2.5 GPa and with the nesting property of the Fermi surface. The observed magnetic moment of the Pr ion is 2 µ B and almost pressure-independent up to at least 4.2 GPa. The 2 µ B magnetic moment originates from the dipole in the low-lying quasi-quartet crystal field state. The pressure-induced antiferromagnetic structure at 3.2 GPa is suppressed by applying a magnetic field of about 1.5 T, which is interpreted as a flop of magnetic moments into the alignment of the ferromagnetic state. This brings about a steep decrease in the electrical resistivity due to the disappearance of the antiferromagnetic superstructure.