Studies of potassium ferrite,K1+xFe11O17. II. Mössbauer effect and spin flopping

The Mössbauer spectrum of the iron analog of K-β-alumina, K_1+xFe₁₁O₁₇, where x = 0.35 to 0.86, has been obtained. Four magnetically split Fe³⁺ components can be resolved. At 295°K the magnetic flux densities at the nuclei are, for the 2a octahedral site 51.8 T, for the 12k octahedral site 43.8 T, and for the two tetrahedral sites, for which an assignment is suggested, 49.5 and 38.7 T. The random distribution of the excess potassium ions resulted in line broadening of the 12k octahedral, and bridging tetrahedral, spectra.Spin flopping in the antiferromagnetic lattice at 4.2°K in an applied magnetic flux density of 2.5 T was inferred from the absence of any effect of the applied field on the spectrum. The consequently low values of the magnetocrystalline anisotropy constants are compared and contrasted with those of the similarly structured ferrimagnetic hexagonal ferrites, and the possible role of Fe²⁺ in reducing the anisotropy is discussed.