Effect of cobalt substitution on magnetic properties of Ba4Ni2-xCoxFe36O60 hexaferrite

Co-substituted U-type hexagonal ferrite bulks, with composition of Ba4Ni2-xCoxFe36 O-60 (x= 0.2, 0.4, 0.6, 0.8), were prepared by a conventional ceramic method. Saturation magnetization (4 pi Ms), coercivity (H-c), and Curie temperature (T-c) were investigated. Anisotropy constant (K-1) was calculated by fitting the magnetization curve (M-H) according to the law of approach to saturation, and anisotropy field (H-a) was calculated accordingly. The results reveal that all the samples possess the U-type hexagonal crystallographic structure. With increasing cobalt substitution content (x), the lattice parameters (a and c) almost remain the same owing to the similar radii of Ni2+ (0.72 angstrom) Co2+ (0.74 angstrom) ions. 4 pi Ms goes up, while H-c H-c shows an opposite trend. K-1 and H-a monotonously decrease resulting from that cobalt substitution weakens the c-axis orientation. Additionally, Tc increases from 467 degrees C to 484 degrees C. (C) 2018 Author(s).