Microstructure and magnetic properties of Co–C nanogranular films

Abstract Nanogranular films of Co–C were fabricated by DC magnetron sputtering at high (30 mTorr) and low (5 mTorr) pressures with Co concentration controlled at about 40 at%. The granular morphology of the as-deposited film remains unchanged, and is altered, respectively, for 30 and 5 mTorr upon annealing. At annealing temperature T a ⩾500 °C, the phase is changed from hexagonal closed-pack (HCP) Co to faulted HCP Co plus FCC Co for 30 mTorr, and to Co 2 C for 5 mTorr. Both the grain size and the coercivity increase with increase in T a for 30 mTorr. The largest H c =381 Oe is obtained at T a =600 °C. Different microstructures and magnetic properties of the films made at the high and low pressures are compared and discussed.