Fabrication of cobalt-iron thin film for magnetic recording head core by electrodeposition and heat treatment

Abstract

According to the dominant soft magnetic properties of CoFe alloy, it has a high potential as soft magnetic films for applications in electrical and electronics industries, especially the writing head core of hard disk drive. However, the knowledge and systematic study to improve the soft magnetic properties of such materials is limited. This research investigates the factors associated with soft magnetic properties of the material produced by electrodeposition and post annealing techniques. The factors of the fabrication include chemical composition, thickness, annealing temperature. These factors are considered with the film's structural elements, namely grain size, roughness, crystallographic orientation, magnetic domain, stress and the applied magnetic field both at room and low temperature. The research is divided into three parts. In Part I, the effects of the chemical composition on the thickness of the electrodeposited CoFe films were studied. It was found that high thickness improves the homogeneity and suppresses defects in the films providing good soft magnetic properties. When the Fe content is low, the texture coefficient at plane (110) and the saturation magnetization is high. Moreover, the grain size is the factor controlling the coercivity of the film. The film with low coercivity contains 'bubble-liked' domain pattern. In Part II, the effect of the stress on the annealed CoFe films were considered. It is found that annealing reduces stress but does not decrease the coercivity due to the increase in uniaxial anisotropy constant. The saturation magnetization varies directly with the texture coefficient of (110) plane. In Part III, the effects of applied magnetic field both at room and low temperature were observed. The in-plane direction of the uniaxial anisotropy reduces the coercivity and varies directly with the grain size while the saturation magnetization depends on the uniaxial anisotropy. Furthermore, the low temperature increases the uniaxial anisotropy constant and the magnetic induction saturation.