Large improvement of coercivity in Sm-(Co,Cu)/Fe films by Cu addition.

The magnetic properties and microstructure of Sm-(Co,Cu)/Fe films were investigated systematically. The addition of Cu is helpful for keeping a better multilayer structure due to the reduction of the crystallization temperature of the hard phase. With lowering the temperature, the coercivity of the Sm-(Co,Cu)/Fe films increases rapidly with a linear relationship. The Cu addition significantly improves the coercivities of the Sm-(Co,Cu)/Fe multilayer films, especially at the low temperatures. Adding the Cu as well as lowering the temperature cause a large inhomogeneity in the hard phase, and therefore a high pinning coercivity.