Molecular Spin-Orbit Excitations In The J(Eff)=1/2 Frustrated Spinel Geco2o4

We describe powder and single-crystal inelastic neutron scattering experiments on a spinel-type antiferromagnet GeCo2O4, represented by an effective total angular momentum J(eff) = 1/2. Several types of nondispersive short-range magnetic excitations were discovered. The scattering intensity maps in Q space are well reproduced by dynamical structure factor analyses using molecular model Hamiltonians. The results of analyses suggest that the molecular excitations below T-N arise from molecular ground states, one of which consists of antiferromagnetically coupled ferromagnetic subunits. 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.