title: Antiferroquadrupolar ordering in a Pr-based superconductor PrIr(2)Zn(20).
abstract: An antiferroquadrupolar ordering at T(Q)=0.11  K has been found in a Pr-based superconductor PrIr(2)Zn(20). The measurements of specific heat and magnetization revealed the non-Kramers Γ(3) doublet ground state with the quadrupolar degrees of freedom. The specific heat exhibits a sharp peak at T(Q)=0.11  K. The increment of T(Q) in magnetic fields and the anisotropic B-T phase diagram are consistent with the antiferroquadrupolar ordered state below T(Q). The entropy release at T(Q) is only 20% of Rln2, suggesting that the quadrupolar fluctuations play a role in the formation of the superconducting pairs below T(c)=0.05  K.
authors.affiliation: Department of Quantum Matter, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima 739-8530, Japan. onimaru@hiroshima-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Onimaru
authors.forename: K T
authors.initials: KT
authors.lastname: Matsumoto
authors.forename: Y F
authors.initials: YF
authors.lastname: Inoue
authors.forename: K
authors.initials: K
authors.lastname: Umeo
authors.forename: T
authors.initials: T
authors.lastname: Sakakibara
authors.forename: Y
authors.initials: Y
authors.lastname: Karaki
authors.forename: M
authors.initials: M
authors.lastname: Kubota
authors.forename: T
authors.initials: T
authors.lastname: Takabatake