Of Copt / C Granular Film Structure And Magnetic Study

As a kind of magnetic recording material, CoPt alloy films have received much attention for it's large anisotropy and coercivity. The space of the intergrains, which can be increased by carbon, can reduce the noise of the media. So CoPt/C nanogranular have been researched widely. Based on the previous study of CoPt/C magnetic recording films,[Co₄₃Pt₅₇ (7 A) / C(8A)]_x (x = 50 - 7) and [Co₅₀Pt₅₀ (9.8 A)/C(8A)]_x (x=10 - 60) samples are deposited by DC magnetron sputtering. The multilayers are annealed at the temperature of700℃ in 4×10^-4Pa for 3 hours to form the nanoparticles. The structure and magneticproperties of the samples before and after annealing are studied.Some conclusions are obtained after investigated the structure and magnetic properties of CoPt/C films.1. The structures of the films:The texture of the films changes markedly after annealing. XRD measurement shows that the texture translates from fcc texture in deposited state to fct texture in annealed state. And AFM measurement shows that annealing destroys the multilayers and forms the granular films.2. The magnetic properties of the films:Coercivity (H_c) and remanence ratio (M_r/M_s) of the deposited films are very low. The samples show soft magnetism. The coercivity and remanence ratio extremely enhance both in plane and out of plane after annealing. Comparing the coercivity of the[Co₄₃Pr₅₇(7A)/C(8A)]_x samples, as well as [Co₅₀pr₅₀(9.8A)/C(8A)]_x samples, a conclusion can be drawn: a large variation of film thickness have little effect on coercivity, Hc remains almost constant. This result is important for improving the magnetic recording density.