2017 Volume 27 Issue 4 Pages 144-147
A cubic 4f2 system PrIr2Zn20 exhibits a superconducting transition at 0.05 K below a quadrupolar transition at 0.11 K. We have conducted neutron diffraction measurements in magnetic fields B ≤ 5 T down to 0.04 K to determine the order parameter expected for the non-Kramers ground state doublet. Field-induced magnetic reflection appears at Q = (1/2, 1/2, –3/2) together with some of its equivalents in B || [1 −1 0]. Thus, the antiferroquadrupole order is characterized by the propagation vector q = (1/2, 1/2, 1/2). The magnetic-structure-factor analysis revealed that the magnetic moments are induced along the [1 1 1] axis on the Pr-ion diamond sublattice. In contrast, no reflections appear for B || [0 0 1] as well as in zero field. The results indicate that the O22-type quadrupole is the primary order parameter which entangles with other various multipolar degrees of freedom. Such entanglements should play the role in the enriched B-T phase diagram of PrIr2Zn20 including the non-Fermi liquid state and field-induced Fermi liquid state.