Tunneling magnetotransport in nanogranular-in-gap structure

Abstract

Monte Carlo modeling was performed to investigate the combined effect of Coulomb blockade and spin-dependent tunneling on charge transport in a granular-in-gap structure, consisting of superparamagnetic Co grains embedded in an insulating matrix between contact electrodes. The tunneling magnetoresistance (TMR) response shows distinct temperature and field dependence, for different types of contacts - nonmagnetic, soft or hard ferromagnetic. These results contrast sharply with predictions by Inoue and Maekawa (1996) based on an infinite granular array, and can be explained by the role of the contacts in the initial rate-determining step.