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

Co-Sm and Co-Pr films were deposited by de magnetron sputtering. Transmissi on electron microscopy and magnetic measurement were used to study the micr ostructure and magnetic propel-ty 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 degrees C, the Co5Sm phas e with the Cu5Ca structure, having grain size of about 20 nm, is obtained a long with high coercivity (45 kOe), The as-deposited Co 22 at. % Sm films a lso have nanostructure similar to the Co 19 at. % films except the volume f raction of the crystallite is reduced. This is related to the concentration of Sm which promotes the formation of the amorphous phase. A new metastabl e phase Co3Sm is formed upon annealing of the Co 22 at. % Sm film at 500 de grees C. This phase has the DO19, structure in which the Sm atoms take orde red positions of a triangular pattern in the close-packed planes. A relativ ely high coercivity value of 29 kOe was obtained from this phase. The as-de posited Go-Pr films show mainly an amorphous phase. Upon annealing at 500 d egrees C for 20 min, Co2Pr with the Mg2Cu-type structure was identified in the Co 35 at. % Pr film. Two phases were identified in the Co 16 at. % Pr f ilms. Coercivities up to 3.1 kOe were achieved in these films, (C) 1998 Ame rican Institute of Physics. [S0021-8979(98)30611-8].