Preparation and Magnetic Properties of Nd³⁺, Al³⁺, Ca²⁺ Substituted M-Type Strontium Hexaferrites

Abstract

Strontium ferrite with Nd³⁺, Al³⁺ and Ca²⁺ substitution of Fe³⁺ and Sr²⁺ ions were prepared by the conventional solid phase reaction process. The Nd³⁺ substitution shows 10 %–20 % improvement in coercivity for the substitution content less than 10 %. The Ca²⁺ substitution is favorable to the enhancement of saturation magnetization due to the accelerated reaction of Fe₂O₃ and SrCO₃. The samples with Al³⁺ substitution of Fe³⁺ show the lowest saturation magnetization, although the highest coercivity was achieved for a homogeneous grain size less than 1 μm. The combinatory substitution Nd³⁺, Ca²⁺ and Al³⁺ leads to the optimum magnetic properties with σ _s=52 A m²/kg and H _cj=412 kA/m.