Magnetisation effects of multicore magnetite nanoparticles crystallised from a silicate glass |
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Authors: | Christian Worsch Peter Schaaf Ruzha Harizanova and Christian Rüssel |
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Affiliation: | (1) Otto-Schott-Institut, Jena University, Fraunhoferstrasse 6, 07743 Jena, Germany;(2) Ilmenau University of Technologie, Gustav-Kirchhoff-Strasse 5, 98684 Ilmenau, Germany;(3) University of Chemical Technology and Metallurgy, Kliment Ohridski Blvd. 8, 1756 Sofia, Bulgaria |
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Abstract: | Magnetic multicore nanoparticles were produced by crystallisation of a glass with the composition Na2O·Al2O3·B2O3·SiO2·Fe2O3. During cooling of the melt, in a first step, phase separation occurred and droplets enriched in boron and iron oxide were formed. These droplets crystallised spontaneously during cooling. The phase-separated droplets had sizes in the range from 200 to 800 nm. Inside the droplets, magnetite crystals with a mean size of 33 nm occurred. Magnetometer measurements showed the occurrence of a small hysteresis which indicates predominantly superparamagnetic behaviour of the magnetite crystals. The magnetic domains of the phase-separated droplets were studied by magnetic force microscopy. In this article, a glass which is exposed to a magnetic field shows droplet-shape phase separations where the single-domain magnetite crystals do not have a preferred orientation of the magnetic dipoles. By contrast, the whole droplet shows one magnetic dipole parallel to the external field if the glass is exposed to a magnetic field during measurement. |
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