Spin Accumulation in Cr Nanoparticles in Single Electron Tunneling Regime

We have studied spin-dependent single electron tunneling in Cr nanoparticles with a diameter of 4 nm using Fe/MgO/Cr-nanoparticles/MgO/Fe double tunnel junctions. The transport properties are governed by the Coulomb blockade, showing suppression of current at low bias voltages. Magnetoresistance is clearly observed at a bias voltage over 0.25 V, and the magnetoresistance ratio increases with increasing bias voltage. These results suggest that the magnetoresistance is due to the spin accumulation in Cr nanoparticles. With some assumption, the minimum value of spin relaxation time in Cr nanoparticles is roughly estimated to be on the order of tens of nanoseconds .