The Influence of Substitution with Aluminum on the Field of Effective Magnetic Anisotropy and the Degree of Magnetic Texture of Anisotropic Polycrystalline Hexagonal Ferrites of Barium and Strontium for Substrates of Microstrip Devices of Microwave Electronics

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This article discusses the influence of substitution with Al³⁺ ions on the field of the effective magnetic anisotropy H_Aeff and the degree of magnetic texture f of anisotropic polycrystalline hexagonal ferrites of barium and strontium. Sample batches are produced by ceramic technology, the texture is formed by compaction in a magnetic field. The preparation of test objects is described in detail. Batches of barium hexaferrites with an ion concentration of Al³⁺ 0.9, 1.4, 2.5, and 2.6 f.u. and batches of strontium hexaferrites with a concentration of 0.1 f.u. are synthesized. It is demonstrated that the applied procedure makes it possible to obtain barium and strontium hexaferrites with H_Aeff = 19–35 kE and f = 80–83%. The mentioned values of H_Aeff and f are sufficient for the production of substrates for microstrip UHV devices of the millimeter wave band. For the first time, it is detected that the degree of the magnetic texture of polycrystalline barium hexaferrites increases with the concentration of Al³⁺ ions; in addition, a moderate magnetic texture (5.5–5.8%) is observed in isotropic strontium hexaferrites. The experimental results are discussed. The formation mechanism of the magnetic texture in the considered hexaferrites during synthesis is proposed.