Magnetic properties of microcrystalline iron (III) oxides and related materials as reflected in their M�ssbauer spectra

The Stardalur magnetic anomaly revisited—New insights into a complex cooling and alteration history

“…Curie temperatures at about 140 °C are 403 reported for ferrihydroxides, e.g. goethite (α FeOOH) at 120 °C (Dunlop and Özdemir, 1997) 404 or ferroxyhite (δ  FeOOH) at 177 °C (Murad, 1996). But ferrihydroxides are not stable during 405 heating to 700 °C, e.g.…”

Transformation of 2-line ferrihydrite to 6-line ferrihydrite under oxic and anoxic conditions

“…Room-temperature Mössbauer measurements, alone, are not adequate to characterize crystallinity of ferrihydrite (Murad 1996) because 2-line ferrihydrite exhibits a doublet feature both at room temperature and 77 K, whereas 6-line ferrihydrite exhibits a doublet only at room temperature. A "collapsed" sextet dominates the spectrum of 6-line ferrihydrite at 77 K (Murad 1996). The presence of a doublet in the room temperature and 77 K spectra of the "fresh" Ni ferrihydrite (Figs.…”

“…5a and 5d). The QS of maximum probability deduced from the QSD corresponds to the average Fe 3+ distortion and the width of the distribution corresponds to the variation in Fe 3+ site geometry (Rancourt 1988;Murad 1996;Rancourt et al 1994). The derived Mössbauer parameters are shown in Table 1.…”

Iron Oxides in a Soil Developed from Basalt

“…In spite of that, some semiquantitative conclusions can be drawn from the results listed in Tables 4 and 5. Some room-temperature M6ssbauer parameters for bulk Mt, Hm, Mh and Im were compiled by Murad and Johnston (1987), Bowen et al (1993) and Murad (1996), and are presented in Table 6 for comparative purpose.…”

“…Murad and Johnston (1987), Bowen et al (1993) and Murad (1996) Goulart et al (1994a). The A1 substitution in the clay Hm, estimated using the equation:…”