Effects of ZnO film thickness on electrical and magnetoresistance characteristics of La0.8Sr0.2MnO3/ZnO heterostructures

The La0.8Sr0.2MnO3/ZnO heterostructures with different thicknesses of ZnO films are fabricated by using RF magnetron sputtering technique. The heterojunctions exhibit excellent rectifying properties at 300 K. At low temperatures the temperature dependent junction resistance exhibits a metal–insulator transition like behavior. A magnetic field strongly impacts on electrical characteristics of La0.8Sr0.2MnO3/ZnO p–n junctions, i.e., depressing the junction resistance greatly and driving the metal–insulator transition temperature (TMI) towards higher temperatures. Large magnetoresistance is observed below TMI, and it increases with increasing magnetic field and almost saturates at 5 T, i.e., above −90% at 100 K and 5 T.