CoPt/C NANOGRANULAR MAGNETIC THIN FILM

Abstract

Granular Co 30 Pt 70/ C and Co 45 Pt 55/ C films, consisting of nanoparticle 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 CoPt 3 and hard CoPt phases and the magnetic interactions between them. High remanence Mr/Ms (>0.8) found in our samples indicates the presence of the intergranular interactions in the samples. Observed positive contributions of δm also give evidence of the existence of exchange interaction. High coercivity and large Mr/Ms make granular CoPt/C film with magnetic nanoparticles very attractive for next-generation high-density recording.