<p>Magnetoplumbite-type (M-type) hexagonal ferrites Ba_0.75−xCa_xLa_0.30Fe₁₂Co_0.25Ti_0.15O₁₉ were synthesized by the solid-state method to examine the effects of Ca/Ba ratio and calcination temperature on structural and magnetic properties. X-ray diffraction confirmed single-phase M-type formation up to x = 0.10, whereas secondary α-Fe₂O₃ appeared at higher Ca contents due to lattice strain and solubility limits. Lattice parameters (a, c) and the c/a ratio showed non-monotonic variation, indicating anisotropic lattice distortion. FE-SEM micrographs revealed platelet-like hexagonal grains consistent with the magnetoplumbite structure. Magnetic measurements exhibited a non-monotonic dependence of saturation magnetization (M_s), remanent magnetization (M_r), and coercivity (Hc) on calcination temperature. An initial decrease in magnetic parameters was followed by enhancement at higher temperatures, attributed to phase evolution, grain growth, and improved magnetic exchange interactions. These results demonstrate that controlled Ca substitution and optimized calcination temperature effectively tailor the magnetic performance of M-type hexaferrites.</p> Graphical abstract <p></p>