Effects of ZnO film thickness on electrical and magnetoresistance characteristics of La sub(0.8)Sr sub(0.2)MnO sub(3)/ZnO heterostructures

The La sub(0.8)Sr sub(0.2)MnO sub(3)/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 La sub(0.8)Sr sub(0.2)MnO sub(3)/ZnO p-n junctions, i.e., depressing the junction resistance greatly and driving the metal-insulator transition temperature (T sub(MI)) towards higher temperatures. Large magnetoresistance is observed below T sub(MI), and it increases with increasing magnetic field and almost saturates at 5 T, i.e., above -90% at 100 K and 5 T.