Preparation and magnetotransport properties of MgO-barrier-based magnetic double tunnel junctions including nonmagnetic nanoparticles

MgO-barrier-based magnetic double tunnel junctions including Au or Cr nanoparticles were prepared by molecular beam epitaxy, and their magnetotransport properties were investigated. A double junction sample including Au nanoparticles showed the Coulomb blockade effect and clear magnetoresistive hysteresis loops. The observed bias voltage dependence of the resistance and magnetoresistance (MR) suggested that the MR effects of 1?2% at high bias voltages were caused by spin accumulation in the Au nanoparticles. In the case of Cr nanoparticles, a double junction with relatively low sample resistance was obtained, showing a clear Coulomb threshold.