Preparation and magnetic characterization of Co2-W strontium hexaferrites doped with Ni and La

The formation and magnetic properties of new Ni- and La-substituted SrCo2-W hexaferrites were investigated. Fabrication of single phase samples required undertaking composition and sintering conditions optimization. This process confirmed the production of W hexaferrites from intermediate cubic and hexagonal ferrite phases and additionally proved the enhancement of final purity by the excessive hexagonal component. Furthermore, according to the X-ray diffraction analysis, pure Ni- or La-doped compounds were formed in most cases, which actually necessitated more intense heat treatment (1225-1250 deg. C). Yet, magnetic measurements interestingly reveal that substances with low substitution possess high saturation magnetization (∼72-75 Am2/kg) and unexpectedly lower coercivity (∼28-46 Oe), compared to the undoped one. This behavior is attributed to the chemistry of both substitutions, inducing the magnetic order variation and the anisotropy transition from in-plane to axial. Thus, a scarcely elaborated transient compositional region with planar anisotropy and strong magnetization is discerned, highlighting the potential of these soft ferrites. - Highlights: → Pure W hexaferrites arise from non-stoichiometric compositions deficient in spinel. → Spin reorientation transition accounts for Ni- and La-doped ferrites' properties. → For low substitution rate, high magnetization and low coercivity occur.