In recent years, a variety of animals have been found which are able to synthesize the ferromagnetic mineral magnetite (Fe 3 O 4). Lowenstam (1962) originally recognized biogenic magnetite in the radular teeth of a primitive marine mollusc, the chiton (Polyplacophora), and since then it has been identified as a precipitate in several magnetically sensitive organisms, including honey bees also r...

The separation factor, aM-0= ( 1 8 0 / 1 6 0 ) magnetite/' ( 1 8 0 / 1 6 0 ) atmospheric oxygen, between the magnetite crust of iron meteorites and atmospheric oxygen has been determined to be 0.9946 ± 0.0005. It is concluded that this fractionation of the oxygen isotopes is the consequence of an equilibrium isotope effect at high temperatures. It can be assumed that this is also valid for cosm...

Water-dispersible Fe(3)O(4) nanoparticles have been prepared by a simple solution method, in which the particle size (3-11 nm) can be tuned by simply adjusting the reaction temperature and time; the formation mechanism of Fe(3)O(4) nanoparticles is proposed and their low cytotoxicity has also been proved.

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Airborne particulate matter (PM) of varying size and composition is known to cause health problems in humans. The iron oxide Fe(3)O(4) (magnetite) may be a major anthropogenic component in ambient PM and is derived mainly from industrial sources. In the present study, we have investigated the effects of four different size fractions of magnetite on signaling pathways, free radical generation, c...

Magnetite is an iron-oxide mineral that occurs naturally on Earth. Because it is also an important component of many anthropogenic materials (e.g., coal fly ash) and synthetic products (e.g., black toner powders), magnetite can be released to the environment through human activities (1). In PNAS,Maher et al. (2) describe the abundant presence in the human brain of magnetite nanoparticles, some ...

Transmission electron microscopy studies have been used to argue that magnetite crystals in carbonate from Martian meteorite ALH84001 have a composition and morphology indistinguishable from that of magnetotactic bacteria. It has even been claimed from scanning electron microscopy imaging that some ALH84001 magnetite crystals are aligned in chains. Alignment of magnetosomes in chains is perhaps...

We report the discovery of exceptionally large biogenic magnetite crystals in clay-rich sediments spanning the Paleocene-Eocene Thermal Maximum (PETM) in a borehole at Ancora, NJ. Aside from previously described abundant bacterial magnetofossils, electron microscopy reveals novel spearhead-like and spindle-like magnetite up to 4 microm long and hexaoctahedral prisms up to 1.4 microm long. Simil...

Studies of the angular dependence of the anisotropic magnetoresistance (AMR) are reported for epitaxial films of magnetite (Fe3O4) grown on MgO (001) and also for single crystals of magnetite. The characteristic feature of the AMR is a two-fold symmetry at temperatures above 200 K. As the samples are cooled below 200 K, an additional set of peaks appears. These become dominant at lower temperat...

We report experimental evidence for the charge-orbital ordering in magnetite below the Verwey transition temperature T(V). Measurements of O K-edge resonant x-ray scattering on magnetite reveal that the O 2p states in the vicinity of the Fermi level exhibit a charge-orbital ordering along the c axis with a spatial periodicity of the doubled lattice parameter of the undistorted cubic phase. Such...