Linear chain antiferromagnetism in FeOHSO4

Magnetic susceptibility measurements on Fe OH SO₄ suggest linear chain antiferromagnetism up to at least 200°K with a transition to three dimensional antiferromagnetism at 56°K. Mössbauer spectra show magnetic hyperfine splitting up to ～ 90°K and this is interpreted in terms of intrachain spin correlation with relaxation effects caused by interchain spin relaxation. The 4·2°K spectrum is strongly asymmetric because of the admixture of nuclear eigenfunctions by non-parallel magnetic and quadrupolar principal axes systems. Using this the first complete derivation of a complete set of hyperfine interaction parameters from a Mössbauer spectrum is made and correlated with the crystallographic structure.