Structure and magnetic properties of co-sputtered Co-C thin films

We studied the structure and magnetic properties of co-sputtered Co_1-xC_x thin films using a transmission electron microscope (TEM) and a SQUID magnetometer. These properties were found to depend critically on deposition temperature, T_S, and composition, x. Generally, phase separation into metallic Co and graphite-like carbon phases proceeds with increasing T_S and decreasing x. Plan view and cross-sectional TEM images of the films prepared showed that Co grains about 10-20 nm in diameter and 30-50 nm in height are three-dimensionally separated by graphite-like carbon layers 1-2 nm thick. Optimum magnetic properties with saturation magnetization of 380 emu/cc and coercivity of 400 Oe were obtained for a film with x = 0.5 and T_S = 350 °C.