Forward and backward diodelike rectifying properties of the heterojunctions composed of La1-x Srx Co O3-δ and 0.7 wt % Nb-doped SrTi O3

Heterojunctions composed of La1-x Srx Co O3-δ (x=0.4 and 0.5) and 0.7 wt % Nb-doped SrTi O3 were fabricated and exhibited good rectifying properties. The asymmetric current-voltage relations for the x=0.4 and x=0.5 junctions display opposite shapes: the former has a forward shape, while the latter shows a backward one. The x=0.4 junction can be viewed as a Schottky diode. For the x=0.5 junction, the forward bias currents show much less temperature dependence than the reverse ones and the reverse voltage Vchar, at which the bias current is 10 μA, displays a distinct change at the ferromagnetic transition temperature of the cobalt oxide of the junction. These observations in the x=0.5 junction can be understood by a nearly degenerate model together with its temperature-dependent magnetism.