Acoustic study for dynamical molecular-spin state without undergoing magnetic phase transition in spin-frustrated ZnFe${}_2$O${}_4$

Abstract

Ultrasound velocity measurements were performed on a single crystal of spin-frustrated ferrite spinel ZnFe${}_2$O${}_4$ from 300 K down to 2 K. In this cubic crystal, all the symmetrically-independent elastic moduli exhibit softening with a characteristic minimum with decreasing temperature below $\sim$100 K. This elastic anomaly suggests a coupling between dynamical lattice deformations and molecular-spin excitations. In contrast, the elastic anomalies, normally driven by the magnetostructural phase transition and its precursor, are absent in ZnFe${}_2$O${}_4$, suggesting that the spin-lattice coupling cannot play a role in relieving frustration within this compound. The present study infers that, for ZnFe${}_2$O${}_4$, the dynamical molecular-spin state evolves at low temperatures without undergoing precursor spin-lattice fluctuations and spin-lattice ordering. It is expected that ZnFe${}_2$O${}_4$ provides the unique dynamical spin-lattice liquid-like system, where not only the spin molecules but also the cubic lattice fluctuate spatially and temporally.

7 pages, 3 figures

References in corpus (9)

• Molecular spin resonance in the geometrically frustrated MgCr2O4 magnet by inelastic neutron scattering
• Emergence of highly degenerate excited states in frustrated magnet MgCr${}_2$O${}_4$
• Molecular spin-orbit excitations in the J_eff = 1/2 frustrated spinel GeCo${}_2$O${}_4$
• Jahn-Teller Inactivity and Magnetic Frustration in GeCo${}_2$O${}_4$ Probed by Ultrasound Velocity Measurements
• Elastic Instabilities within Antiferromagnetically Ordered Phase in the Orbitally-Frustrated Spinel GeCo${}_2$O${}_4$
• 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$$
• Spin-orbit fluctuations in frustrated heavy-fermion metal LiV${}_2$O${}_4$
• Molecular spin-liquid state in spin-3/2 frustrated spinel HgCr${}_2$O${}_4$
• Multiple lattice instabilities resolved by magnetic-field and disorder sensitivities in cubic paramagnetic phase of the orbital-degenerate frustrated spinel MgV${}_2$O${}_4$

Cited by in corpus (5)

• Orbital- and spin-driven lattice instabilities in quasi-one-dimensional CaV${}_2$O${}_4$
• A variety of elastic anomalies in orbital-active nearly-itinerant cobalt vanadate spinel
• 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)