The segregation structure of electroless-plated CoNiReP alloy films for perpendicular magnetic recording media was investigated, and the origin of coercivity variation at the initial deposition is discussed. Two types of films were used, i.e., film A had a low perpendicular coercivity, Hc(⊥), of several hundred Oe at a thin region less than 0.1 µm, while film B had a high Hc(⊥) of over 1.4 kOe at the region. Although a value of saturation magnetization, Ms, indicating segregation of magnetic components, was different for each of the as-plated films, the Ms value was almost the same after a 400°C heat-treatment. This is assumed to be due to the occurrence of crystallization and segregation in the films with heat-treatment, and also because the same segregated structure was attained in the two films. In the case of the very thin 0.1 µm film, a larger change of Ms value in film A was observed than in the 0.5 µm film. Thus, the higher degree of segregation was assumed in the thinner region of film B. The high coercivity in the thinner film B was due to the enhanced segregation of the components which occurred during the heat-treatment.
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