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

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 mu m. The combinatory substitution Nd3+, Ca2+ and Al3+ leads to the optimum magnetic properties with sigma (s)=52 A m(2)/kg and H (cj)=412 kA/m.