CoPt/C nanogranular magnetic thin film

Granular Co30Pt70/C and Co45Pt55/C films, consisting of nanopaxticle CoPt phases embedded in a carbon matrix, have been made by co-sputtering from CoPt and C targets using a tandem deposition mode. X-ray diffraction shows the existence of hard CoPt phase embedded in an amorphous C matrix after annealing. The coercivities for CoPt/C are strongly dependent on C and Pt composition. Films with coercivity of up to 5.4 kOe and grain size of 7 nm can be obtained. The development of shoulder in hysteresis loop may be contributed to the co-existence of magnetic Soft COPt3 and hard CoPt phases and the magnetic interactions between them. High remanence M-T/M-8 (> 0.8) found in our samples indicates the presence of the intergranular interactions in the samples. Observed positive contributions of delta m also give evidence of the existence of exchange interaction. High coercivity and large M-T/M-8 make granular CoPt/C film with magnetic nanoparticles very attractive for next-generation high-density recording.