Preparation of an Exchange-Biased Fe-Based Amorphous Soft-Magnetic Underlayer

Abstract

Fe-based amorphous soft-magnetic films and Mn-Ir exchange-biasing films were investigated, with the aim of developing a soft-magnetic underlayer for L1₀-type Fe-Pt perpendicular double-layered media. It was found that a carbon-added Fe₇₈Si₉B₁₃ composition film had a smooth surface and excellent structural stability in amorphous state after annealing at 450°C. A B_s value of 13.7 kG and an H_c value of below 1 Oe for the easy axis were obtained. For the exchange-biased films, the compositions and crystal orientations of the Mn-Ir films and the effects of inserting a Co-Fe layer between the Fe-Si-B-C layer and the Mn-Ir layer were investigated. As a result, a large unidirectional anisotropy constant, J_k, of 0.5 erg/cm² was obtained for a layer configuration of Fe-Si-B-C (50 nm)/Co₇₀Fe₃₀ (5 nm)/Mn₈₅Ir₁₅ (10 nm)/Nb-Permalloy (5 nm)/Ta(20 nm)/glass-substrate. The large exchange-bias field, small coercivity, smooth surface, and excellent structural stability of the film will be suitable for the soft-magnetic underlayer of Fe-Pt media.