Magnetochrome-catalyzed oxidation of ferrous iron by MamP enables magnetite crystal growth in the magnetotactic bacterium AMB-1.

Magnetotactic bacteria have evolved the remarkable capacity to biomineralize chains of magnetite [Fe(II)Fe(III)O] nanoparticles that align along the geomagnetic field and optimize their navigation in the environment. Mechanisms enabling magnetite formation require the complex action of numerous proteins for iron acquisition, sequestration in dedicated magnetosome organelles, and precipitation into magnetite. The MamP protein contains c-type cytochromes called magnetochrome domains that are found exclusively in magnetotactic bacteria.

Magnetic anisotropy engineering in onion-structured metal oxide nanoparticles combining dual exchange coupling and proximity effects.

A series of exchange-coupled magnetic nanoparticles combining several magnetic phases in an onion-type structure were synthesized by performing a three-step seed-mediated growth process. Iron and cobalt precursors were alternatively decomposed in high-boiling-temperature solvents (288-310 °C) to successively grow CoO and FeO shells (the latter in three stages) on the surface of FeO seeds. The structure and chemical composition of these nanoparticles were investigated in depth by combining a wide panel of advanced techniques, such as scanning transmission electron microscopy (STEM), electron energy-loss spectroscopy-spectrum imaging (EELS-SI), Fe Mössbauer spectrometry, and X-ray circular magnetic dichroism (XMCD) techniques.

Influence of organic ligands on the stoichiometry of magnetite nanoparticles.

Magnetite, a ubiquitous mineral in natural systems, is of high interest for a variety of applications including environmental remediation, medicine, and catalysis. If the transformation of magnetite to maghemite through the oxidation of Fe has been well documented, mechanisms involving dissolution processes of Fe in aqueous solutions have been overlooked. Here, the effect of dissolved organic ligands (EDTA (ethylenediaminetetraacetic acid), acetic, lactic and citric acids) on Fe solubility and on the stoichiometry (Fe(ii)/Fe(iii)) of magnetite-maghemite nanoparticles (∼10 nm) was investigated.

Comparative Study on the Magnetic and Transport Properties of B-Site Ordered and Disordered CaCuFeOsO.

The B-site Fe/Os ordered and disordered quadruple perovskite oxides CaCuFeOsO were synthesized under different high-pressure and high-temperature conditions. The B-site ordered CaCuFeOsO is a system with a very high ferrimagnetic ordering temperature of 580 K having the Cu(↑)Fe(↑)Os(↓) charge and spin arrangement. In comparison, the highly disordered CaCuFeOsO has a reduced magnetic transition temperature of about 350 K.

Quantum Advantage in a Molecular Spintronic Engine that Harvests Thermal Fluctuation Energy.

Recent theory and experiments have showcased how to harness quantum mechanics to assemble heat/information engines with efficiencies that surpass the classical Carnot limit. So far, this has required atomic engines that are driven by cumbersome external electromagnetic sources. Here, using molecular spintronics, an implementation that is both electronic and autonomous is proposed.