Buffer layer-enhanced magnetic field effect in manganite-based heterojunctions

Influence of magnetic field on the rectifying property of the La0.67Ca0.33MnO3/LaMnO3/SrTiO3:0.05 wt %Nb heterojunctions has been studied. In addition to an enhanced magnetic response of the current-voltage characteristics, a field-induced increase in junction resistance, which is an effect different from that in the junctions without the LaMnO3 layer, is observed.

The positive magnetoresistance is further found to show a systematic variation with the thickness of the LaMnO3 layer (t), growing rapidly with the increase of layer thickness and getting a maximum of ∼91% at t=4 nm (T=50 K and ΔH=5 T). Analysis of the current-voltage and capacitance-voltage characteristics indicates a field-induced growth of interfacial barrier, which is responsible for the abnormal effect observed here.