Enhanced tunnel magnetoresistance in granular nanobridges

We have fabricated granular nanobridge structures consisting of electrodes separated by a nanometer-sized gap in which a thin insulating CoAlO granular film is filled, and measured the current-bias voltage characteristics in a magnetic field to investigate the spin-dependent transport. The Coulomb blockade with a clear threshold voltage (V-th) is observed at 4.2 K. Tunnel magnetoresistance (TMR) is enhanced by fabricating nanobridges. TMR shows a maximum exceeding about 30% at the voltage slightly above V-th. This enhancement is explained by the orthodox theory of single electron tunneling in ferromagnetic multiple tunnel junctions. (C) 2001 American Institute of Physics.