Coulomb staircase and tunnel magnetoresistance in nanowire-shaped granular films

Spin-dependent single-electron tunneling properties have been studied in nanostructured samples consisting of nonmagnetic electrodes with a nanogap and (Co-Pt)-Al-O granular films. The granular films were formed into a nanowire shape by electron-beam lithography and Ar ion milling in order to restrict current channels bridging between electrodes. Clear Coulomb staircases have successfully been observed due to the sufficient restriction of current channels in a granular nanowire. Tunnel magnetoresistance as a function of bias voltage shows oscillatory behavior with sign change, suggesting spin-dependent single-electron tunneling with spin accumulation in Co-Pt nanoparticles.