Coulomb blockade effects on magnetoresistance of granular magnetic media

Abstract

A full Monte Carlo simulation is performed of the magnetotransport across a granular system of Co nanoparticles, embedded in an insulating Al 2O 3 matrix. The interplay between spin-dependent tunneling and Coulomb blockade effects is modeled using the so-called "orthodox" theory of single-charge tunneling. The tunneling magnetoresistance ratio (TMR) shows a strong temperature dependence, especially for the case of nonmagnetic contact electrodes. This behavior contradicts previous predictions by Inoue and Maekawa [Phys. Rev. B 53, 11927 (1996)], and can be explained by considering the crucial role of the initial rate-determining tunneling step. © 2002 American Institute of Physics.