Observation of elastic anomalies driven by coexisting dynamical spin Jahn-Teller effect and dynamical molecular-spin state in the paramagnetic phase of frustrated MgCr 2O 4

Tadataka Watanabe, Shin Ichi Ishikawa, Haruki Suzuki, Yusuke Kousaka, Keisuke Tomiyasu

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Ultrasound velocity measurements of the magnesium chromite spinel MgCr 2O 4 reveal elastic anomalies in the paramagnetic phase that are characterized as due to geometrical frustration. The temperature dependence of the tetragonal shear modulus (C 11-C 12)/2 exhibits huge Curie-type softening, which should be the precursor to spin Jahn-Teller distortion in the antiferromagnetic phase. The trigonal shear modulus C 44 exhibits nonmonotonic temperature dependence with a characteristic minimum at ∼50 K, indicating a coupling of the lattice to a dynamical molecular-spin state. These results strongly suggest the coexistence of the dynamical spin Jahn-Teller effect and a dynamical molecular-spin state in the paramagnetic phase, which is compatible with the coexistence of magnetostructural order and a dynamical molecular-spin state in the antiferromagnetic phase.

Original languageEnglish
Article number144413
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume86
Issue number14
DOIs
Publication statusPublished - 2012 Oct 22

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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