Cooperative Jahn-Teller Phase Transition in the Nickel-Zinc-Chromite System

Kino, Yoshihiro; Lüthi, B.; Mullen, Michael

doi:10.1143/jpsj.33.687

Cited by 78 publications

(23 citation statements)

References 13 publications

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“…T dependence of elastic modulus C Γ (T ) in the orbital JT systems is explained assuming the coupling of ultrasound to JT-active ions via the crystal-field striction mechanism, and the presence of inter-JT-activeion interactions. A mean-field expression of C Γ (T ) in the orbital JT systems is given as: [23][24][25]…”

Section: A Curie-type Softening In Pm Phasementioning

confidence: 99%

Observation of elastic anomalies driven by coexisting dynamical spin Jahn-Teller effect and dynamical molecular-spin state in the paramagnetic phase of frustrated MgCr2O4

et al. 2012

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Ultrasound velocity measurements of magnesium chromite spinel MgCr2O4 reveal elastic anomalies in the paramagnetic phase that are characterized as due to geometrical frustration. The temperature dependence of the tetragonal shear modulus (C11 − C12)/2 exhibits huge Curie-type softening, which should be the precursor to spin Jahn-Teller distortion in the antiferromagnetic phase. The trigonal shear modulus C44 exhibits nonmonotonic temperature dependence with a characteristic minimum at ∼50 K, indicating a coupling of the lattice to dynamical molecular spin state. These results strongly suggest the coexistence of dynamical spin Jahn-Teller effect and dynamical molecular spin state in the paramagnetic phase, which is compatible with the coexistence of magnetostructural order and dynamical molecular spin state in the antiferromagnetic phase.

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Section: A Curie-type Softening In Pm Phasementioning

confidence: 99%

Observation of elastic anomalies driven by coexisting dynamical spin Jahn-Teller effect and dynamical molecular-spin state in the paramagnetic phase of frustrated MgCr2O4

et al. 2012

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“…Taking into account the intersite quadrupole-quadrupole interaction, the quadrupole-strain interaction in Eq. ͑1͒ leads to the temperature dependence of the JT-active elastic modulus C ⌫ 3 = C 11 −C 12 2 in the cubic phase T Ͼ T N , written as [13][14][15] …”

Section: A Shear Modulimentioning

confidence: 99%

“…Ultrasound velocity is a powerful tool for the study of orbital physics because electric quadrupole moments of JT ions strongly couple to the lattice deformations. [12][13][14][15] In addition, since ultrasound wave modulates the distance between magnetic ions, ultrasound velocity is also a directional probe of the anisotropy of exchange interactions acting on the magnetic phase transition. 16 The present study discusses orbital state, spin state, and possible magnetic frustration in GeCo 2 O 4 from the elastic properties.…”

Section: Introductionmentioning

confidence: 99%

Jahn-Teller inactivity and magnetic frustration inGeCo2O4probed by ultrasound velocity measurements

2008

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Ultrasound velocity measurements of cubic spinel GeCo 2 O 4 in single crystal were performed for the investigation of shear and compression moduli. The shear moduli in the paramagnetic state reveal the absence of Jahn-Teller activity despite the presence of orbital degeneracy in the Co 2+ ions. Such a Jahn-Teller inactivity indicates that the intersite orbital-orbital interaction is much stronger than the Jahn-Teller coupling. The compression moduli in the paramagnetic state near the Néel temperature T N reveal that the most relevant exchange path for the antiferromagnetic transition lies in the ͓111͔ direction. This exchange-path anisotropy is consistent with the antiferromagnetic structure with the wave vector q ʈ ͓111͔, suggesting the presence of bond frustration due to competition among a direct ferromagnetic interaction and several distant-neighbor antiferromagnetic interactions. In the Jahn-Teller-inactive condition, the bond frustration can be induced by geometrical orbital frustration of t 2g -t 2g interaction between the Co 2+ ions, which can be realized in the pyrochlore lattice of the high-spin Co 2+ with t 2g -orbital degeneracy. In GeCo 2 O 4 , the tetragonal elongation below T N releases the orbital frustration by quenching the orbital degeneracy.

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“…The difference between these numbers yields an estimate for the increase in lattice energy ∆ H l = 0.24(7) meV/Cr. The energy associated with simple tetragonal strain [23] only accounts for v 0 (c 11 (ǫ 2 c +2ǫ 2 a )/2+c 12 (ǫ 2 a +2ǫ a ǫ c )) = 0.026 meV/Cr so there are likely additional modifications to the structure of ZnCr 2 O 4 below T c that help to stabilize Néel order.…”

mentioning

confidence: 99%

Local Spin Resonance and Spin-Peierls-like Phase Transition in a Geometrically Frustrated Antiferromagnet

et al. 2000

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Inelastic magnetic neutron scattering reveals a localized spin resonance at 4.5 meV in the ordered phase of the geometrically frustrated cubic antiferromagnet ZnCr2O4. The resonance develops abruptly from quantum critical fluctuations upon cooling through a first order transition to a co-planar antiferromagnet at T(c) = 12. 5(5) K. We argue that this transition is a three dimensional analog of the spin-Peierls transition.

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Cooperative Jahn-Teller Phase Transition in the Nickel-Zinc-Chromite System

Cited by 78 publications

References 13 publications

Observation of elastic anomalies driven by coexisting dynamical spin Jahn-Teller effect and dynamical molecular-spin state in the paramagnetic phase of frustrated MgCr2O4

Observation of elastic anomalies driven by coexisting dynamical spin Jahn-Teller effect and dynamical molecular-spin state in the paramagnetic phase of frustrated MgCr2O4

Jahn-Teller inactivity and magnetic frustration inGeCo2O4probed by ultrasound velocity measurements

Local Spin Resonance and Spin-Peierls-like Phase Transition in a Geometrically Frustrated Antiferromagnet

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