Observation of elastic anomalies driven by coexisting dynamical spin Jahn-Teller effect and dynamical molecular spin state in paramagnetic phase of the frustrated MgCr${}_2$O${}_4$$

Abstract

Ultrasound velocity measurements of magnesium chromite spinel MgCr${}_2$O${}_4$ 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 $\sim$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.

arXiv comment6 pages, 3 figures

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Cited by in corpus (16)

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• Emergence of highly degenerate excited states in frustrated magnet MgCr${}_2$O${}_4$
• Berezinskii-Kosterlitz-Thouless Type Scenario in Molecular Spin Liquid $A$Cr${}_2$O${}_4$
• Spin Jahn-Teller antiferromagnetism in CoTi${}_2$O${}_5$
• Acoustic study for dynamical molecular-spin state without undergoing magnetic phase transition in spin-frustrated ZnFe${}_2$O${}_4$
• FeTi${}_2$O${}_5$: a spin Jahn-Teller transition enhanced by cation substitution
• Multiple lattice instabilities resolved by magnetic-field and disorder sensitivities in cubic paramagnetic phase of the orbital-degenerate frustrated spinel MgV${}_2$O${}_4$
• Anisotropic phase diagram and spin fluctuations of the hyperkagome magnet Gd3Ga5O12 as revealed by sound velocity measurements
• A variety of elastic anomalies in orbital-active nearly-itinerant cobalt vanadate spinel
• Orbital- and spin-driven lattice instabilities in quasi-one-dimensional CaV${}_2$O${}_4$
• Orientation-dependent stabilization of MgCr${}_2$O${}_4$ spinel thin films
• Softening of breathing elastic mode and trigonal elastic mode in disordered pyrochlore magnet NaCaCo${}_2$F${}_7$
• Symmetry-resolved elastic anomalies in spin-crossover cobaltite LaCoO${}_3$
• Elastic softness of low-symmetry frustrated $A$Ti${}_2$O${}_5$ ($A$ = Co, Fe)
• Thermally-induced mimicry of quantum cluster excitations and implications for the magnetic transition in FePSe${}_3$
• Magnetoelastic coupling at the field-induced transition in EuAl${}_{12}$O${}_{19}$