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A Transmission Electron Microscopy Study of Fe-Co Alloy Nanoparticles in Silica Aerogel Matrix Using HREM, EDX, and EELS

  • Andrea Falqui (a1) (a2), Anna Corrias (a1), Mhairi Gass (a3) and Gavin Mountjoy (a1)

Abstract

Magnetic nanocomposite materials consisting of 5.5 wt% Fe-Co alloy nanoparticles in a silica aerogel matrix, with compositions FexCo1−x of x = 0.50 and 0.67, have been synthesized by the sol-gel method. The high-resolution transmission electron microscopy images show nanoparticles consisting of single crystal grains of body-centered cubic Fe-Co alloy, with typical crystal grain diameters of approximately 4 and 7 nm for Fe0.5Co0.5 and Fe0.67Co0.33 samples, respectively. The energy dispersive X-ray (EDX) spectra summed over areas of the samples gave compositions FexCo1−x with x = 0.48 ± 0.06 and 0.68 ± 0.05. The EDX spectra obtained with the 1.5 nm probe positioned at the centers of ∼20 nanoparticles gave slightly lower concentrations of Fe, with means of ⟨x⟩ = 0.43 ± 0.01 and ⟨x⟩ = 0.64 ± 0.02, respectively. The Fe0.5Co0.5 sample was studied using electron energy loss spectroscopy (EELS), and EELS spectra summed over whole nanoparticles gave x = 0.47 ± 0.06. The EELS spectra from analysis profiles of nanoparticles show a distribution of Fe and Co that is homogeneous, i.e., x = 0.5, within a precision of at best ±0.05 in x and ±0.4 nm in position. The present microscopy results have not shown the presence of a thin layer of iron oxide, but this might be at the limit of detectability of the methods.

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Corresponding author. E-mail: g.mountjoy@kent.ac.uk

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Permanent address: School of Physical Sciences, University of Kent, Canterbury, Kent CT2 7NH, UK

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References

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Abeles, B. (1976). Granular metal films. In Applied Solid State Science, Wolfe, R. (Ed.), pp. 1117. New York: Academic Press.
Brinker, C.J. & Scherer, G.W. (1990). Sol-Gel Science. San Diego, CA: Academic Press.
Carta, D., Mountjoy, G., Gass, M., Navarra, G., Casula, M.F. & Corrias, A. (2007). Structural characterization study of FeCo alloy nanoparticles in a highly porous aerogel silica matrix. J Chem Phys 127, 204705.
Casu, A., Casula, M.F., Corrias, A., Falqui, A., Loche, D., Marras, S. & Sangregorio, C. (2008). The influence of composition and porosity on the magnetic properties of FeCo-SiO2 nanocomposite aerogels. Phys Chem Chem Phys 10, 10431052.
Casula, M.F., Concas, G., Congiu, F., Corrias, A., Falqui, A. & Spano, G. (2005). Near equiatomic FeCo nanocrystalline alloy embedded in an alumina aerogel matrix: Microstructural features and related magnetic properties. J Phys Chem B 109, 2388823895.
Casula, M.F., Loche, D., Marras, S., Paschina, G. & Corrias, A. (2007). Role of urea in the preparation of highly porous nanocomposite aerogels. Langmuir 23, 35093512.
Cliff, G. & Lorimer, G.W. (1975). The quantitative analysis of thin specimens. J Microsc 103, 203207.
Egerton, R.F. (1996). Electron Energy-Loss Spectroscopy in the Electron Microscope, pp. 210216. New York: Plenum Press.
Ennas, G., Casula, M.F., Falqui, A., Gatteschi, D., Marongiu, G., Piccaluga, G., Sangregorio, C. & Pinna, G. (2001). Nanocrystalline iron-cobalt alloys supported on a silica matrix prepared by the sol-gel method. J Non-Cryst Solids 293-295, 19.
Falqui, A., Serin, V., Calmels, L., Snoeck, E., Corrias, A. & Ennas, G. (2003). EELS investigation of FeCo/SiO2 nanocomposites. J Microsc 210, 8088.
Gich, M., Casas, L., Roig, A., Molins, E., Sort, J., Surinach, S., Baro, M.D., Munoz, J.S., Morellon, L., Ibarra, M.R. & Nogue, S. (2003). High-coercivity ultralight transparent magnets. Appl Phys Lett 82, 43074309.
Guillermet, A.F. (1988). Critical evaluation of the thermodynamic properties of the Fe-Co system. High Temp High Press 19, 477499.
Husing, N. & Schubert, U. (1998). Aerogels airy materials: Chemistry, structure, and properties. Angew Chem Int Ed 37, 2245.
Li, J.S., Mirzamaani, M., Bian, X.P., Doerner, M., Duan, S.L., Tang, K., Toney, M., Arnoldussen, T. & Madison, M. (1999). 10 Gbit/in.2 longitudinal media on a glass substrate. J Appl Phys 85, 42864291.
MacLaren, J.M., Schulthess, T.C., Butler, W.H., Sutton, R. & McHenry, M.J. (1999). Electronic structure, exchange interactions, and Curie temperature of FeCo. J Appl Phys 85, 48334835.
Moreno, E.M., Zayat, M., Morales, M.P., Serna, C.J., Roig, A. & Levy, D. (2002). Preparation of narrow size distribution superparamagnetic gamma-Fe2O3 nanoparticles in a sol-gel transparent SiO2 matrix. Langmuir 18, 49724978.
Paduani, C. & Krause, J.C. (1999). Electronic structure and magnetization of Fe-Co alloys and multilayers. J Appl Phys 86, 578583.
Pierre, A.C. & Pajonk, G.M. (2002). Chemistry of aerogels and their applications. Chem Rev 102, 42434265.
Saad, A.M., Mazanik, A.V., Kalinin, Y.E., Fedotova, J.A., Fedotov, A.K., Wrotek, S., Sitnikov, A.V. & Svito, I.A. (2004). Structure and electrical properties of CoFeZr-aluminium oxide nanocomposite films. Rev Adv Mater Sci 8, 152157.
Williams, D.B. & Carter, C.B. (1996). Transmission Electron Microscopy, vol. 4, pp. 608611. New York: Plenum Press.

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