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MA: Magnetismus

MA 6: Magnetische Partikel / Cluster

MA 6.10: Vortrag

Montag, 8. März 2004, 17:30–17:45, H10

Equation of State of Fe₃C nanoparticles — •E. Duman, M. Acet, T. Hülser, and E.F. Wasserman — Experimentalphysik, AG Farle, Universität Duisburg-Essen

Fe₃C, which incorporates only Fe as a metallic element with valence electron concentration e/a = 8, is an Invar material [1]. The p electrons of the interstitial carbon atoms hybridize with the d-band of the metal, so that the electron concentration per Fe atom becomes 8.67 for Fe₃C, which fits into the Invar composition range. We have measured the pressure dependence up to 30 GPa of the lattice parameters of Fe₃C nanoparticles (∼ 40 nm) at room temperature and at 550 K using energy dispersive X-ray diffraction. The pressure-volume data was analysed with the third order Birch-Murnaghan equation and the isothermal bulk modulus of both samples were obtained at room temperature and 550 K. The bulk modulus of Fe₃C nanoparticles at room temperature (B_o=201 GPa) was found to be approximately %14 smaller than that of the value at 550 K (B_o= 235 GPa). This difference is comparable with the relative difference in the bulk modulus of Fe₆₅Ni₃₅ Invar in a similar temperature range [2]. No pressure or temperature induced phase transition was observed. Supported by DFG (SFB 445) [1]W. Pepperhof, M. Acet, Constitution and Magnetism of Iron and its Alloys, Springer- Verlag, Berlin-Heidelberg, 2001 [2]Philippe Renaud, Ph. D Thesis, Universite de Lausanne, Faculte des Sciences, 1988