Anomalous magnetization behaviour in a single crystal of vanadium spinel FeV2O4.

Spinel oxide FeV2O4, having the orbital degrees of freedom at Fe(2+) and V(3+) ions, exhibits multi-step magnetic phase transitions and successive structural phase transitions at low temperatures. In order to clarify the magnetic properties of FeV2O4, we have measured the temperature dependence of magnetization, isothermal magnetization curves and specific heat using a single crystal of FeV2O4. Temperature-induced magnetization jumps below the 110 K were observed in the zero-field-cooled magnetization curves. Furthermore, we found that the behaviours of the isothermal magnetization curves were quite different between the zero-field-cooled and field-cooled conditions. We suggest that the change of the magnetic domain structure under the magnetic field associated with the orbital states of Fe(2+) ions is the possible origin of these intriguing and anomalous magnetic properties in a single crystal of FeV2O4.