Crystal chemical and magnetic studies of garnet systems M32+Fe 2Sn 3O 12—Y 3Fe 2Fe 3O 12

Abstract

A complete solid-solution range exists in the system Ca 3Fe 2Sn 3O 12(CIS)—Y 3Fe 2Fe 3O 12 (YIG). Because of its large size, the Sn 4+ ion prefers the octahedral positions; thus for dilute solutions of CIS in YIG the saturation magnetization at 0°K increases. A maximum of 7.3 μ b per formula unit is reached at about 20 mol. percent CIS solid solution. However, the plot of n b (∞, 0) vs. composition deviates markedly from that which depends only on a simple interaction model. At 33 mol. per cent CIS, n B = 5.2 μ B , and at 50 mol. per cent, n B = 1.2 μ B , even though the Sn 4+ ions are very nearly all in the octahedral sites. At 67 mol. per cent CIS, 90 per cent of the octahedral sites are filled with Sn 4+ ions, as determined by X-ray diffraction, and n B ≈ 0.25 μ B . The magnetic behavior of this system may be explained on the basis of the reduction of the number of octahedraltetrahedral magnetic-ion interactions with increasing concentration of CIS and, at the higher concentrations, the establishment of two magnetic sublattices among the tetrahedral ions. No other end-members M 3 2+Fe 2Sn 3O 12 were obtained, but with M = Sr the extent of solubility in YIG is ∼ 33 mol. per cent, and when M = Ba, < 5 mol. per cent. Some inconclusive experiments also indicated some solution when M = Cd, Zn, Mn, Ni and Mg.