Tunneling spin polarization of Ni clusters embedded in rare gas matrices

The tunneling magnetoresistance (TMR) of granular films made of well-defined Ni clusters (mean diameter ≈4.5nm) embedded in the rare gas matrices Kr and Xe has been measured as a function of temperature (1.7K⩽T⩽30K). The spin polarization P of the tunneling electrons as obtained from TMR(T=0) is P=20(1)%. This value is compared with those obtained from other tunneling experiments.