Nanospectroscopy highlights

Despite being the oldest known magnetic material, magnetite is attracting renewed scientific and technological interest in view of spintronics applications. For the realization of practical devices, it is of utmost importance to control the material's magnetic properties in the case the reduced dimensionality limit is approached, as it occurs in thin films or nanostructures, aiming at obtaining stable anisotropy and magnetization. Although magnetite thin films are widely studied, the minimum thickness at which ferrimagnetic behavior can be observed is still under debate. In fact, most thin film studies are performed by separate growth and characterization experiments, which are typically carried out using laterally averaging techniques. To solve this fundamental problem we have exploited the current capabilities of photoelectron spectromicroscopy, and characterized the structural, chemical and magnetic properties of selected magnetite nanocrystals. Through the combined use of low energy electron microscopy,

X-ray photoemission microscopy, and X-ray circular dichroism photoemission electron microscopy we successfully monitored the growth of a single magnetite nanocrystal in real time while characterizing its crystal structure, surface stoichiometry and magnetic behavior. In this way, we have been able to find out that magnetite is ferromagnetic at room temperature at a thickness of only one nanometer, in what may be the thinnest lodestone ever.

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Magnetism in nanometer-thick magnetite;
M. Monti, B. Santos, A. Mascaraque, O.R. de la Fuente, M.A. Niño, T.O. Menteş, A. Locatelli, K.F. McCarty, J.F. Marco, J. de la Figuera;
Phys. Rev. B 85, 020404(R) (2012);
doi: 10.1103/PhysRevB.85.020404.