Regensburg 2002 – scientific programme

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MA: Magnetismus

MA 19: Spinstrukturen und magnetische Phasenübergänge (incl. Sensoren(19.11) und Messmethoden(19.12-13))

MA 19.4: Talk

Thursday, March 14, 2002, 16:00–16:15, H23

Magnetisation Studies and Random Field Effects in U_1−xPu_xSb 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

Single crystals of three concentrations x of U_1−xPu_xSb have been grown by the mineralisation technique. They were found to crystallise in the cubic sodium chloride structure. After encapsulation, magnetisation and susceptibility measurements have been done in the three main crystallographic directions. Effective moments µ_eff and paramagnetic Curie temperatures are determined, as well as Néel temperatures for the transition to the magnetically ordered phase. For x=0.25 and x=0.50 the magnetic structure is the same as in USb. Special attention has been given to U_0.25Pu_0.75Sb. Two transitions are observed in these samples, one to a triple k^→ structure below 93 K, and a second one to a region with mixed triple k^→ and single k^→ character below 55 K. Magnetisation curves in this low temperature region look rather complicated and are understood by taking into account the random distribution of uranium and plutonium ions onto the lattice sites. The random field model for two different kinds of magnetic ions can explain the unusual shape of magnetisation curves for U_1−xPu_xSb.