Influence of Co on microstructure and coercivity of (Ni0.5Fe0.5)80B10Si2Cu1Zr7 alloy

Abstract The effects of Co on microstructure, crystallization behavior and magnetic properties of (Ni0.5Fe0.5-xCox)80B10Si2Cu1Zr7 (x = 0~0.5) alloys were investigated. The results show that, the as-spun alloys remain lower coercivity (Hc) values (5 A/m ~ 14 A/m) over the whole Co content range, owing to their amorphous structure. After being annealed for 20 min above the onset temperatures of primary crystallization (Tx1), amorphous and nanocrystallines are coexisted in the alloys, and the crystal structure of nanocrystallines changes between fcc-(Ni, Fe, Co) and bcc-(Fe, Ni, Co) with the increasing Co content. In particular, it was found that Hc of the annealed alloys changes anomalously between 40 A/m and 1529 A/m with the increasing Co content, owing to the integrated action of grain size (D), magnetocrystalline anisotropy (K1) and lattice distortion. Especially for the alloys with x = 0.2 and x = 0.3, serious lattice distortion is the dominant factor for their higher Hc value than 1000 A/m.