Phase formation and magnetic properties of Co-rare earth magnetic films

Co–Sm and Co–Pr films were deposited by dc magnetron sputtering. Transmission electron microscopy and magnetic measurement were used to study the microstructure and magnetic property relationship. The nanostructure of the as-deposited Co 19 at. % Sm films consists of two phases: the amorphous phase and the crystallite phase. Upon annealing at 600 °C, the Co5Sm phase with the Cu5Ca structure, having grain size of about 20 nm, is obtained along with high coercivity (45 kOe). The as-deposited Co 22 at. % Sm films also have nanostructure similar to the Co 19 at. % films except the volume fraction of the crystallite is reduced. This is related to the concentration of Sm which promotes the formation of the amorphous phase. A new metastable phase Co3Sm is formed upon annealing of the Co 22 at. % Sm film at 500 °C. This phase has the DO19 structure in which the Sm atoms take ordered positions of a triangular pattern in the close-packed planes. A relatively high coercivity value of 29 kOe was obtained from this ph...