Spin-Dependent Single-Electron Tunneling Phenomena

摘要

Spin-dependent single-electron tunneling was investigated in microfabricated granular systems. Two types of sample structures were fabricated: granular nanobridges and GPP geometry structures. The granular nanobridge consists of electrodes separated by a nanometer-sized gap filled with a thin insulating Co{sub}36Al{sub}22O{sub}42 granular film. Coulomb blockade with a clear threshold voltage (V{sub}th) is observed at 4.2K, and the tunnel magnetoresistance (TMR) is enhanced at a voltage slightly above Vth. This enhancement is consistent with the calculation using the orthodox theory of single-electron tunneling in ferromagnetic multiple junctions. The CPP geometry structure consists of a thin Co{sub}36Al{sub}22O{sub}42 granular film sandwiched by top and bottom electrodes with a submicron-sized contact area. Clear Coulomb staircases are observed, and the tunnel magnetoresistance (TMR) shows oscillatory behavior associated with the Coulomb staircase.