1 Department of Physics, Technical University of Denmark2 Experimental Surface and Nanomaterials Physics, Department of Physics, Technical University of Denmark3 Chuo University4 Teikyo University5 Chuo University6 Teikyo University
The structure and magnetism of Fe2(OH)[B2O4(OH)] are reported. Powder x-ray diffraction reveals a characteristic structure containing two crystallographically independent zigzag-ladder chains of magnetic Fe2+ ions. Magnetization measurements reveal a phase transition at 85 K, below which a weak spontaneous magnetization (approximate to 0.15 μB/Fe) appears. Below 85 K, magnetization increases with decreasing temperature down to 70 K, below which it decreases and approaches a constant value at low temperature. The Mossbauer spectrum at room temperature is composed of two paramagnetic doublets corresponding to the two crystallographic Fe2+ sites. Below 85 K, each doublet undergoes further splitting because of the magnetic hyperfine fields. The temperature dependence of the hyperfine field is qualitatively different for the two distinguishable Fe2+ sites. This is responsible for the anomalous temperature dependence of the magnetization.
Journal of Physics-condensed Matter, 2014, Vol 26, Issue 26
Crystal structure; magnetization; Mössbauer spectroscopy; Iron oxide