Large negative magnetoresistance and ferromagnetism induced by interfacial spins in granular Cr/C films

Cr/C composite films with 7.9 and 8.5 at% Cr contents were fabricated by facing-target magnetron sputtering. Cr nanoparticles are embedded in amorphous carbon matrix, and Cr atoms bond with C atoms at the interface. The Cr/C films were found to exhibit ferromagnetism in the temperature range of 2-300 K, which is probably induced by uncompensated spins at the surface of Cr nanoparticles. Spin-dependent magnetoresistance (up to −19.5% at 90 kOe and 2 K) was observed in the Cr/C films. The negative MR originates from the alignment of the uncompensated spins at the interface between nanoparticles and matrix. The spin polarization which comes from the interfacial p-d hybridization was calculated to be 21% and 17% in the Cr/C films with 7.9% and 8.5% Cr, respectively.