Spin-dependent conductance minima in magnetic tunnel junctions

We present a study on the positions of conductance minima for the parallel and antiparallel magnetization configurations in magnetic tunnel junctions, both experimentally and theoretically. It is found that the conductance minima can have as much as a 100-mV shift from zero bias, and the shifts are spin dependent. These behaviors have not been observed in tunnel junctions based on nonmagnetic electrodes. By considering the voltage dependent density of states of ferromagnetic electrodes in the Brinkman model, the difference can be well explained. The results demonstrate that the density of states of the ferromagnetic electrodes play an important role in defining the bias dependence behaviors in magnetic tunnel junctions. (C) 2003 American Institute of Physics.