Abstract
The principal and average magnetic susceptibilities of FeSiF6,6H2O and FeGeF6,6H2O have been measured in the temperature range 300–80 °K. Theoretical magnetic moments have been calculated for a free-ion 5D basis, perturbed by a trigonal crystal-field and spin–orbit coupling. A crystal field (D3d) point-charge calculation was parameterized by the second- and fourth-order radial parameters Cp and Dq, and an angular parameter θ. For Cp > Dq the mixing of the two trigonal 5Eg terms by spin–orbit coupling and the crystal field altered the theoretical principal magnetic moments from those calculated for a 5T2g cubic-field basis set. The low experimental moments of the complexes [as compared to the near tetragonal (NH4)2Fe(SO4)2,6H2O] derives from the sensitivity of the ground-state splitting, Δ, to θ when Cp is large: and this appears to be characteristic of the trigonal nature of the distortion. Assuming λ=kλ0 and Dq= 1000 cm.–1 ambiguous fits with ranges of values of Cp, k, and θ have been found. It was not possible to resolve these ambiguities by use of optical, Mossbauer, or e.s.r. spectra.The magnetic properties of the 5D term perturbed by a tetragonal crystal-field and spin–orbit coupling, have been briefly investigated and susceptibilities of Fe(NH4)2(SO4)2,6H2O discussed.
Published Version
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