Elastic Instabilities within Antiferromagnetically Ordered Phase in the Orbitally-Frustrated Spinel GeCo${}_2$O${}_4$

Abstract

Ultrasound velocity measurements of the orbitally-frustrated GeCo${}_2$O${}_4$ reveal unusual elastic instabilities due to the phonon-spin coupling within the antiferromagnetic phase. Shear moduli exhibit anomalies arising from the coupling to short-range ferromagnetic excitations. Diplike anomalies in the magnetic-field dependence of elastic moduli reveal magnetic-field-induced orbital order-order transitions. These results strongly suggest the presence of geometrical orbital frustration which causes novel orbital phenomena within the antiferromagnetic phase.

5 pages, 3 figures

References in corpus (5)

• Molecular spin resonance in the geometrically frustrated MgCr2O4 magnet by inelastic neutron scattering
• Magnetic frustration in the spinel compounds Ge Co_2 O_4 and Ge Ni_2 O_4
• Doubly degenerate orbital system in honeycomb lattice: implication of orbital state in layered iron oxide
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• Jahn-Teller Inactivity and Magnetic Frustration in GeCo${}_2$O${}_4$ Probed by Ultrasound Velocity Measurements