Single-crystal growth and magnetic properties of Co-substituted Ca–La magnetoplumbite-type ferrite

• Published in: Journal of solid state chemistry 2019-02, Vol.270, p.366-369
• Main Authors: Waki, T., Uji, K., Tabata, Y., Nakamura, H.
• Format: Article
• Language: English
• Subjects: Ca–La–Co magnetoplumbite-type ferrite; Magnetic anisotropy; Permanent magnet; Self-flux method; Single crystal
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2018.11.036

Using the flux method, we successfully synthesized Co-substituted Ca–La magnetoplumbite-type ferrite single crystals, CaxLayFezCowO19 (Ca–La–Co system), a base material for high-performance hard ferrite magnets. Wavelength-dispersive X-ray analysis revealed that the chemical compositions of the obtained crystals depended on both the starting composition and reaction atmosphere. The fraction of Fe + Co to Ca + La deviates from the canonical value of 12, and the Co content, which is essential in magnetic anisotropy, improves with the synthesis under an oxygen gas stream. In addition, the magnetic anisotropy is enhanced by the Co substitution, as expected, but also depends on the Ca/La ratio, suggesting an appreciable effect of Fe2+. The magnetocrystalline anisotropy can be larger in the Ca–La–Co system than in the Sr–La–Co system. Anisotropy field, HA, at 5 K for the Co-substituted Ca–La magnetoplumbite-type ferrite, CaxLayFezCowO19, plotted against Co content w. Literature data of the Sr–La–Co system are also plotted for comparison. [Display omitted] •Successful synthesis of Co-substituted Ca-La magnetoplumbite-type ferrite single crystals.•Enhancement in the magnetic anisotropy by the Co substitution.•Magnetocrystalline anisotropy larger than the Sr-La-Co ferrites .