In this study, the carbon additive Co-Fe-Zr-B alloy films were prepared by dual-gun co-sputtering. The effects of the carbon addition and heat treatment on the nanostructure and magnetic properties of the Co-Fe-Zr-B-C alloy films are reported. The experimental results show that a crystalline (Co, Fe) phase formed after heat treatment at 400 in the Co-Fe-Zr-B-C films with low carbon additive level. Carbon atoms inhibited the of the as-deposited Co-Fe-Zr-B-C films. From the TEM observation the nanostructures. such as the atomic structure and grain sizes, showed a strong carbon content dependence. The coercivities of the Co-Fe-Zr-B-C films annealed at 400 varied from 18 to 0.3 Oe with the increasing carbon addition. However, the films annealed at higher temperature exhibited a dramatic increase in the coercivities, which correlated to the formation of the crystalline (Co, Fe) phase. The resistivities of the Co-Fe-Zr-B-C films relied on the carbon contents rather than on annealing temperatures. (c) 2009 Elsevier B.V. All rights reserved.