Percolative spin-dependent transport in mesoscopic epitaxial fe plaquettes of tailored connectivity

Abstract

Spin-dependent charge transport in a two-tier granular system consisting of mesoscopic Fe plaquettes over which silver nanospheres are dispersed is investigated. This system transits from a coulomb blockade regime with a finite voltage threshold for charge flow to an infinitely connected network showing dynamic resistance as the area coverage by Ag is increased. The zero-bias conductance (G_V=0) of the system at low coverage is thermally activated with an energy U ( 33 meV) equivalent to the charging energy of the Ag spheres. The current-voltage curves in this regime show power-law scaling with ξ≈2.2. A small (≈0.8%) but distinct low-field (≈0.2 T) magnetoresistance establishes the spin dependence of the coulomb energy U.