Quadrupole and lattice effects of orbitally degenerate 4f-electron systems

Terutaka Goto, Mitsuhiro Akatsu, Tatsuya Yanagisawa, Takashi Yamaguchi, Yuichi Nemoto, Osamu Suzuki, Shintaro Nakamura, Satoru Kunii, Ryuta Watanuki, Kazuya Suzuki

Research output: Contribution to journalArticlepeer-review


The quadrupole orderings and lattice effects in 4f-electron systems with orbital degeneracy in rare earth compounds have been investigated by ultrasonic and thermal expansion measurements. A ferroquadrupole (FQ) Oxy-type ordering associated with a trigonal distortion in HoB6 with a Γ5 ground state is presented. The trigonal distortion in ordered phase IV CexLa1-xB6 (x = 0.75 and 0.70) with a Γ8 ground state indicates Oxy-type FQ ordering in phase IV. In both systems, HoB6 and CexLa1-xB6. C44 anomalies are observed. In tetragonal HoB2C2, an ordered phase IV appears near a tetra-critical point, where the antiferroquadrupole phase II and antiferromagnetic phase III compete with each other. Noticeable ultrasonic attenuation and softening of elastic constants in phase IV of HoB2C2 due to quadrupole fluctuation with a slow relaxation time τ ∼ 7 × 10-9 s are found.

Original languageEnglish
Pages (from-to)S2101-S2107
JournalJournal of Physics Condensed Matter
Issue number28
Publication statusPublished - 2003 Jul 23


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