ABSTRACT
Magnetic tunnel junctions consist of two Co electrodes separated by A1,0,, in which one or several layers of Co nanoparticles are embedded, are fabricated and studied. The shapes of the Co nanoparticles are shown by TEM to be close to spherical and the blocking temperature is about 30 K. A good magnetic tunnel junction shows a non-linear current-voltage (I-V) curve and the tunneling probability depends on the relative orientation of the moments in the two electrodes. Since the junction has non-linear I-V curves, V-biased and I-biased magnetoresistance (MR) are different. The ratio between I-biased and V-biased MR depends on the curvature of the I-V curve, which in turn depends on the physical properties of the insulating barrier. The existence of Co nanoparticles inside the insulating barrier gives rise to Coulomb blockade effect at low temperature. Our results show MR does not change significantly crossing blocking temperature, but I-biased MR is strongly suppressed at low bias, low temperature.
