Effects of Fe Substitution by Ni on the Structural, Morphological, and Magnetic Properties of SrFe10−xNixAl₂O19 Hexaferrites

M-type strontium hexaferrite SrFe[Formula: see text]Ni[Formula: see text]Al 2 O[Formula: see text] ([Formula: see text], 0.1, 0.2 and 0.3) magnetic powders were prepared by sol–gel auto-combustion method. Their structural, morphological, and magnetic properties were investigated. The prepared powders were calcined at 1200 ∘ C for 3[Formula: see text]h X-ray powder diffraction. The results confirmed that the samples were single-phase, with P63/mmc space group. The average crystallite size was found in the range of 43.94–39.80[Formula: see text]nm. The Scanning Electron Microscopy shows that the grain size ranges from 0.33[Formula: see text][Formula: see text]m to 0.26[Formula: see text][Formula: see text]m. The magnetic properties were studied by analyzing the hysteresis cycles ([Formula: see text]–[Formula: see text]. The substitution of Fe by Ni led to a reduction in both coercive field and saturation magnetization. These changes in magnetic properties are correlated with the structural alterations induced by substituting iron ions with nickel ions. The Law of Approach to Saturation (LAS) was used to extract key magnetic parameters, notably the effective anisotropy constant ([Formula: see text], giving information about the magnetic behavior of our samples.