Crystal structure and magnetic properties of Sr1 − x Sm x Fe12 − x Co x O19 solid solutions

Abstract

Sr1 − x Sm x Fe12 − x Co x O19 (0 ≤ x ≤ 0.5) ferrites have been prepared by solid-state reactions in air at 1470 K using mixtures of samarium oxide, ferric oxide, Co3O4, and strontium carbonate. X-ray diffraction characterization showed that the samples with x < 0.2 were single-phase, whereas the samples with 0.2 ≤ x ≤ 0.5 contained α-Fe2O3 and those with 0.3 ≤ x ≤ 0.5 contained SmFeO3, CoFe2O4, and Sm2O3 as well. The highest degree of Sm3+ and Co2+ substitutions for Sr2+ and Fe3+ (x) in the SrFe12O19 ferrite at 1470 K was determined to be slightly less than 0.2. This substitution only slightly decreases the a and c parameters of the hexagonal lattice and the Curie temperature (T C) of the material. At temperatures of 5 and 300 K in magnetic fields of up to 14 T, we obtained magnetic hysteresis loops, which were used to evaluate the spontaneous magnetization (σ0), specific saturation magnetization (σs), and coercive force (σ H c) of the ferrites. The experimentally determined 5-K spontaneous magnetization per formula unit (n 0) of the x = 0.1 ferrite is 20.86μB, which coincides with the theoretical value calculated as n 0 = (8 × 5) − (3.9 × 5 − 0.1 × 3) = 20.8μB. At 300 K, the n 0 and σ H c of Sr0.9Sm0.1Fe11.9Co0.1O19 exceed those of SrFe12O19 by 7.7 and 9.9%, respectively.