Abstract
The spinel oxides γ-Fe2O3, which are widely used for magnetic recording applications, have a quite low coercivity. For pure γ-Fe2O3, the coercivities lie between around 100 Oe for spherical grains, and 400 Oe, for well-shaped submicronic acicular particles. Berthollide oxides powders (1-x)γ-Fe2O3-xFe3O4 can reach higher values because of the magnetocrystalline anisotropy of Fe2+ ions. However, the coercivities are generally limited to 500 Oe. Significant improvements that allow coercivities to reach more than 1000 Oe can be obtained when small quantities of divalent cobalt ions are introduced into the bulk or located at the surface of the particles. In this paper, we present results concerning new iron oxide pigments CuFe2O4, CoxCu1-xFe2O4 (0<x≤1) and MnxFe3-xO4+δ (1<x≤2). These pigments are tetragonally distorted spinel oxides and they have a high coercivity (>1000 Oe), even when they are free of divalent iron or cobalt ions. The high level of coercivity is studied in correlation with the tetragonal distortion of the unit cell.
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Villette, C., Agnoli, F., Bonino, C., Tailhades, P., Rousset, A. (1997). Coercivity Enhancement in CuFe2O4 and MnXFe3-XO4 (1<X≤2) Due to Oxidation and Jahn-Teller Distortion. In: Hadjipanayis, G.C. (eds) Magnetic Hysteresis in Novel Magnetic Materials. NATO ASI Series, vol 338. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-5478-9_41
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DOI: https://doi.org/10.1007/978-94-011-5478-9_41
Publisher Name: Springer, Dordrecht
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