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Co-substituted U-type hexagonal ferrite bulks, with composition of Ba4Ni2−xCoxFe36O60 (x=0.2, 0.4, 0.6, 0.8), were prepared by a conventional ceramic method. Saturation magnetization (4πMs), coercivity (Hc), and Curie temperature (Tc) were investigated. Anisotropy constant (K1) was calculated by fitting the magnetization curve (M-H) according to the law of approach to saturation, and anisotropy field (Ha) 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 Å) Co2+ (0.74 Å) ions. 4πMs goes up, while HcHc shows an opposite trend. K1 and Ha monotonously decrease resulting from that cobalt substitution weakens the c-axis orientation. Additionally, Tc increases from 467 °C to 484 °C. [ABSTRACT FROM AUTHOR]

A highly textured M-type barium hexa-ferrite (BaM) quasi-single crystal was fabricated by a magnetic forming plus liquid participation sintering technique. Its grain orientation degree was determined to be 97.3% with the tile angle no more that 5°. The magnetization behavior from its angular magnetic hysteresis loops was very similar to that of a BaM single crystal. Moreover, the feasibility of practical utilization of the as-fabricated BaM quasi-single crystal in low-field biased circulators was certificated by a simulation method. [ABSTRACT FROM AUTHOR]

We report the magnetic and structural properties of a series of W-type barium hexaferrites of composition BaZn2-xCoxFe16O27, where x = 0.15, 0.20, and 0.25. The anisotropy field of these barium ferrites (BaW) decreased with the substitution of divalent Co ions, while they maintained crystallographic c-axis texture. The measured anisotropy field was ∼10 kOe, and a hysteresis loop squareness Mr/Ms = 79% was obtained due to well-controlled grain size within the range of single domain scale. These two properties make the BaW suitable for applications in microwave devices at lower frequencies, such as self-biased circulators operated at X-band frequencies. [ABSTRACT FROM AUTHOR]