The transformation behavior of M-type barium ferrites due to Co–Ti substitution

In this paper, we synthesized Co–Ti equiatomic co-substitution of M-type barium ferrites [BaFe_12−2x(CoTi)_xO₁₉, x = 1.00–1.30 with step of 0.05] by solid state reaction method. All samples exhibited a single-phase M-type barium ferrite structure, compared with pure M-type barium ferrite (x = 0.00). With increasing of Co–Ti content, saturation magnetization (M _s) decreased, gradually. However, coercivity (H _c) appeared decreased first and then increased after x = 1.20. The minimum value of coercivity was 258.08 Oe at x = 1.20. Meanwhile, magnetic permeability (μ) also first increased to a high value and then decreased rapidly after x = 1.20. The maximum value of μ reached about 25 (at x = 1.10). The appropriate contents of Co–Ti substitution makes the magnetocrystalline anisotropy transform from uniaxial to planar anisotropy. Due to Co–Ti substitution, the magnetocrystalline anisotropy constant decreases from a high value and reach a minimum value, and changes from positive to negative value, increases oppositely, this determines the changes of magnetic properties.