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arXiv · 1102.4395

Molecular spin-orbit excitations in the J_eff = 1/2 frustrated spinel GeCo$_2$O$_4$

K. Tomiyasu·M. K. Crawford·D. T. Adroja·P. Manuel·A. Tominaga·S. Hara·H. Sato·T. Watanabe·S. I. Ikeda·J. W. Lynn·K. Iwasa·K. Yamada
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Abstract

We describe powder and single-crystal inelastic neutron scattering experiments on a spinel-type antiferromagnet GeCo$_2$O$_4$, represented by an effective total angular momentum J_eff = 1/2. Several types of non-dispersive short-range magnetic excitations were discovered. The scattering intensity maps in $\vec{Q}$ space are well reproduced by dynamical structure factor analyses using molecular model Hamiltonians. The results of analyses strongly suggest that the molecular excitations below T_N arise from a hidden molecular-singlet ground state, in which ferromagnetic subunits are antiferromagnetically coupled. The quasielastic excitations above T_N are interpreted as its precursor. A combination of frustration and J_eff = 1/2 might induce these quantum phenomena.

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K. Tomiyasu, M. K. Crawford, D. T. Adroja, P. Manuel, A. Tominaga, S. Hara, H. Sato, T. Watanabe, S. I. Ikeda, J. W. Lynn, K. Iwasa, K. Yamada. 2011-02-22. Molecular spin-orbit excitations in the J_eff = 1/2 frustrated spinel GeCo$_2$O$_4$. https://doi.org/10.1103/physrevb.84.054405

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