On the transition point of thermally activated conduction of spinel-type MFe2O4 ferrite thin films (M=Zn, Co, Ni)

摘要: Thin films of zinc ferrite (ZnFe2O4), cobalt ferrite, and nickel have been grown on SrTiO3(100) substrates. By changing the growth temperature TG, electrical conductivity σ thin can be switched from insulating to conducting. An increased lattice constant at low temperatures (e.g., TG(ZnFe2O4)<450 °C) indicates formation defects, which seems promote hopping conductivity. Temperature-dependent measurements reveal two thermally activated conduction processes. Interestingly, transition point these processes Tx=107 K−140 K is close Verwey known structurally similar magnetite films.