Magnetic Frustration Driven by Itinerancy in Spinel CoV2O4

Localized spins and itinerant electrons rarely coexist in geometrically-frustrated spinel lattices. They exhibit a complex interplay between localized spins and itinerant electrons. In this paper, we study the origin of the unusual spin structure of the spinel CoV2O4, which stands at the crossover from insulating to itinerant behavior using the first principle calculation and neutron diffraction measurement. In contrast to the expected paramagnetism, localized spins supported by enhanced exchange couplings are frustrated by the effects of delocalized electrons. This frustration produces a non-collinear spin state even without orbital orderings and may be responsible for macroscopic spin-glass behavior. Competing phases can be uncovered by external perturbations such as pressure or magnetic field, which enhances the frustration

Magnetic susceptibility and specific heat of a spinel MnV2O4 single crystal

We investigated the magnetic and the thermodynamic properties of a spinel MnV2O4 single crystal. The magnetization and susceptibility show the signature of ferromagnetic ordering at similar to 61 K. A sharp peak in the magnetization and the specific heat indicate the structural phase transition at 58 K, consistent with the scattering experiments. The specific-heat data exhibits the signature of double transitions. In addition to the higher-temperature transition at T-S, the second transition occurs at a lower temperature T*, which divides the phase below T-S into a low-magnetic-field and a high-magnetic-field phase. Based on the magnetic susceptibility and the specific heat, a wide-range temperature and magnetic-field phase diagram was constructed. The low-magnetic-field phase shows the characteristics of a spin-glass-like state. A comparison with the magnetic and thermodynamic characteristics of similar materials suggests that the low temperature and low-magnetic-field, spin-glass-like phase in MnV2O4 may originate from the competition between the interchain and the intrachain exchange interaction owing to the fluctuating V-ion orbitals.open112024sciescopu