Magnetic tunnel junctions with a zinc oxide-cobalt oxide composite tunnel barrier

Composite CoO-ZnO tunnel junctions showing nonlinear and asymmetric current-voltage characteristics with significant magnetoresistance ratios (up to 8% at 77 K) have been prepared by using reactive sputtering from a zinc target. Electron transmission microscopy demonstrates the formation of a zinc oxide-cobalt oxide bilayer. Observed asymmetries, which are directly linked to the difference in zinc oxide and cobalt oxide barrier heights are in good agreement with calculations done within the framework of a parabolic bands model, using thicknesses extracted from transmission electron microscopy (TEM) images and barrier heights found in literature. (C) 2005 American Institute of Physics.