Magnetic properties of permanent magnets based on M-type strontium ferrite with Sr <sup>2+</sup> substituted by Sm <sup>3+</sup> and Gd <sup>3+</sup> and Fe <sup>3+</sup> substituted by Zn <sup>2+</sup> and Co <sup>2+</sup>
Sr 1-xLn xFe 12-xM x0 19 (Ln 3+ - Sm 3+, Gd 3+; M 2+ - Co 2+, Zn 2+) and (Ba 0,5Sr 0,5) 1-xSm xFe 12-xCo x0 19 (x = 0; 0,1; 0,2; 0,3) ferrites have been prepared by solid-state method in air at 1473 K. It has been shown that isotropic permanent magnets based on Sr 0,9Sm 0,1Fe 11,9Co 0,1О 19, (Ba 0,5Sr 0,5) 0,9Sm 0,1Fe 11,9Co 0,1О 19 ferrites show higher values of magnetic induction (B r), coercive force ( BH c) and maximum energy product (BH) max than ones based on SrFe l20 19 ferrite. It has been found that using SrFe 9,5Al 2,50 19 as an additive increases the coercive force ( BH c) and maximum energy product (BH) max for isotropic permanent magnets from the solid solutions of Sr 0,9Sm 0,1Fe 11,9 Co 0,1О 19, (Ba 0,5Sr 0,5) 0,9Sm 0,1Fe 11,9Co 0,1О 19 ferrites.