High coercivity Co and Co-Ni alloy films

A high coercivity and a high hysteresis loop squareness pure Co and Co-Ni (up to 50 at %) alloy films have been prepared by a new process. The new process involves the films, including N, being sputter deposited in an atmosphere of Ar-N2 mixture and annealed at temperature above 553 K. Most of the included N diffuses out from the film surface after annealing, and the films have a strong preferred orientation with the c axis parallel to the film plane. In Co70Ni30 alloy films, a high coercivity Hc of 1 kOe (80 kA/m) and a high hysteresis loop squareness S* of 0.95 are achieved. The values of Hc gradually decrease as the Ni/Co concentration ratio of the films departs from 30/70. There is a strong correlation between Hc and the preferred orientation of crystallites; Hc increases as the c axis orientation parallel to the film plane grows.