Magnetic properties of feroxyhyte (?-FeOOH)

Abstract

Abstract. Magnetization curves and high-field M6ss-bauer spectra are used to deduce a model for the magnetic order in synthetic samples of 6-FeOOH (feroxyhyte), which takes account of the changes in magnetization when the samples are heated at 105 ~ Feroxyhyte is essentially a planar antiferromagnet with the net sublattice moments aligned parallel or antiparallel to c. Each particle acquires a net moment due to the very small number of layers along the c-direction, and the presence of surface steps causing the formation of ferrimagnetic domains with an odd number of layers. There is some spin canting which is related to the crystallinity of the sample. The decrease in magnetization following heating is mainly due to an increase in the extent of antiferromagnetic coupling between the closely packed ferrimagnetic particles, but changes in the spin canting within the bulk may also contribute. A typical, rather well crystallized specimen has magnetization a = 14 JT-1 kg-1 and Curie temperature T~ = 455 K.

Elucidation of the electrochromic mechanism of nanostructured iron oxides films

“…4, the gradual blue shift of the absorption edge with the cycle number can be associated with a transformation of hematite to an oxyhydroxide. Unlike all the other iron oxyhydroxides, the d-FeOOH phase is ferrimagnetic [23,25,26]. The transformation to d-FeOOH is also confirmed with magnetic measurements.…”

Enhanced magnetization of the Marlboro Clay as a product of soil pyrogenesis at the Paleocene–Eocene boundary?

“…7c). The Marlboro Clay sample (WLB 361.0) has a dominant phase that continues to unblock just above 600 • C, perhaps attributable to maghemite; there is also an inflection in the demagnetization curve at around 200 • C, which could correspond to feroxyhyte, a magnetic mineral with the same composition as goethite but which is a ferrite with a Curie temperature of around 180 • C (Harrison and Feinberg, 2009;Koch et al, 1995). In contrast, thermal demagnetization of the initial IRM for the Vincentown sample (WLB 371.7) shows a dominant phase that unblocks at ∼350 • C, probably the sulfide greigite, and a subsidiary phase that unblocks at ∼580 • C and is thus most likely magnetite (Harrison and Feinberg, 2009).…”

Magnetic water treatment

“…For example, FeOOH has a plate-like morphology with a net moment when an odd number of ferromagnetic layers are coupled antiferromagnetically [7]. The energy ( ) MB of superparamagnetic clusters will be of the order of 1 J/mol.…”