Bias voltage effect on tunnel magnetoresistance in fully epitaxial MgO double-barrier magnetic tunnel junctions

Double-barrier magnetic tunnel junctions (DMTJs), consisting of a fully epitaxial Fe(001)/MgO(001)/Fe(001)/MgO(001)/Fe(001) structure, have been deposited onto MgO (001) single-crystal substrates using molecular-beam epitaxy, and have been characterized by measuring the bias voltage effects on both tunneling magnetoresistance (TMR) and conductance. The DMTJs are found to show large TMR ratios of up to 110% and extremely small bias voltage dependence (V-half= 1.44 V under a positive bias application) compared with conventional magnetic tunnel junctions (MTJs) with a single MgO barrier at room temperature. In addition, clear asymmetry is observed in the bias voltage dependence of the TMR ratios with respect to the signs of the bias, which corresponds to the asymmetric bias dependence of the conductance, especially for a parallel magnetization configuration. Such a high V-half with a large TMR ratio is relevant for a high-output MTJ cell for future spintronic devices. (c) 2005 American Institute of Physics.