Tunnel magnetoresistance oscillations in current perpendicular to plane geometry of CoAlO granular thin films

We have fabricated current-perpendicular-to-plane geometry samples consisting of a thin CoAlO granular film sandwiched by top and bottom electrodes with a submicron-sized contact area, and measured magnetotransport properties at 4.2 K. Clear Coulomb staircases due to the charging effect of Co granules are observed by the addition of an Al-O bottleneck layer which leads to an asymmetric configuration of tunnel resistances. Furthermore, tunnel magnetoresistance (TMR) shows oscillatory behavior associated with the Coulomb staircase. It is considered that the TMR oscillation is based on the interplay of spin-dependent tunneling and single electron tunneling. (C) 2002 American Institute of Physics.