Regensburg 2002 – wissenschaftliches Programm

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MA: Magnetismus

MA 10: Poster : Dünne Schichten(1-21),Spinabh.Transp.(22-39),Exch.Bias(40-51),Spindyn.(52-55),Mikromag.(56-66),Partikel(67-74),Abb.Verf.(75-77),Oberfl.+Spinelektr.+Elektr.Theo+Mikromag(75-87),PÜ+Aniso+Werkst/Leg.(88-103),Mol.Mag.+N-dim+Messm.+Postdead(104-111

MA 10.50: Poster

Dienstag, 12. März 2002, 15:00–19:00, Bereich A

Magnetisation studies on U_1−xPu_xO₂ single crystals — •D. Kolberg^1,2, F. Wastin¹, J. Rebizant¹, and J. Schoenes² — ¹European Commission, Joint Research Centre, Institute for Transuranium Elements, Postfach 2340, 76125 Karlsruhe — ²Institut für Halbleiterphysik und Optik, Technische Universität Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig

Mixed uranium-plutonium dioxides are important for their use as reactor fuel, and the corner compounds UO₂ and PuO₂ show unusual solid state properties. Single crystals of U_1−xPu_xO₂ have been grown for a large range of concentrations from x=0.05 to x=0.95 by means of chemical vapor transport reaction. Magnetisation and susceptibility data were taken on encapsulated samples using a commercial SQUID magnetometer. Ordering temperatures T_N have been determined as well as paramagnetic Curie temperatures Θ_P and effective magnetic moments µ_eff. We found a rather complicated behaviour for Θ_P and µ_eff as a function of x. Spin-lattice interactions manifest themselves in non-linearities of the observed 1/χ vs. T curves from which we are able to suggest different mechanisms for the interactions as a function of the constituent’s concentrations. From our susceptibility measurements characteristic parameters have been calculated using a model of tetragonal vibrational modes of the oxygen cage surrounding each uranium ion. These include specific spin-lattice coupling parameters G, mode characteristic temperatures T_ω, and molecular field constants λ.