TY - JOUR
T1 - 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
AU - Watanabe, Tadataka
AU - Ishikawa, Shin Ichi
AU - Suzuki, Haruki
AU - Kousaka, Yusuke
AU - Tomiyasu, Keisuke
PY - 2012/10/22
Y1 - 2012/10/22
N2 - 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.
AB - 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.
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U2 - 10.1103/PhysRevB.86.144413
DO - 10.1103/PhysRevB.86.144413
M3 - Article
AN - SCOPUS:84867779175
SN - 0163-1829
VL - 86
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
IS - 14
M1 - 144413
ER -