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

Autor: Tomiyasu, K., Crawford, M. K., Adroja, D. T., Manuel, P., Tominaga, A., Hara, S., Sato, H., Watanabe, T., Ikeda, S. I., Lynn, J. W., Iwasa, K., Yamada, K.
Rok vydání: 2011
Předmět:
Zdroj: Phys. Rev. B 84, 054405 (2011)
Druh dokumentu: Working Paper
DOI: 10.1103/PhysRevB.84.054405
Popis: 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.
Comment: 7 pages, 4 figures, submitted to Phys. Rev. B
Databáze: arXiv