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

Abstract 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.