Resistive hysteresis and capacitance effect in NiFe2O4/SrTiO3: Nb(1 wt%) junctions

Epitaxial ultrathin NiFe2O4 films were deposited on 1 wt% Nb-doped SrTiO3 (0 0 1) substrates by reactive cosputtering to form junctions with an area of ∼2 mm2, and current–voltage curves show rectifying and asymmetrical hysteresis characteristics. The resistance calculated from the current–voltage curves is strongly voltage dependent, and the hysteretic loops with high and low resistive states were observed. The hysteretic loops are considered to stem from the capacitance effect of the highly resistive NiFe2O4 layer, which leads to charge accumulation at the interfaces. The results show that the interfaces of the junctions have a large areal capacitance of ∼100 nF/mm2 from 300 to 120 K.