Unveiling the Lattice Site Modification and Magnetic Behavior in Sr 1‐ x Ca x Fe 12‐ y In y O ₁₉

The hexagonal lattice of M‐type hexaferrite is susceptible to complete substitution of Ca 2+ /In 3+ for ( x , y ) = (0.1, 1.0). The substitution induced a distortion at the polyhedral site within the crystal structure, as evidenced by changes in the Fe‐O bond length and the Fe‐O‐Fe bond angle. Relatively, the preferential occupancy of In 3+ is higher at the octahedral sites of Fe 3+ . The initial magnetization curve shows a transition from concave to convex with the introduction of In 3+ in the Fe 3+ site. Effective magnetocrystalline anisotropy, coercivity, and magnetization are found to decrease in substituted samples. The DC permeability is increased at lower applied magnetic fields upon substitution, as observed in the virgin magnetization curve, with a crossover near 6 kOe. The variation of DC permeability reflects the symmetry of the hysteresis loop. The softening effect of magnetic anisotropy is characterized by a reduced value of magneto‐crystalline anisotropy. The H c decreased from 5.57 to 1.71 kOe with magnetic dilution. The reduced strength of the superexchange interaction is correlated with the modifications of the lattice sites. The flattening of ΔH vs. M confirms that magnetization reversal is symmetric and requires lower energy.