Regensburg 2010 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 21: Magnetic Materials

MA 21.1: Vortrag

Mittwoch, 24. März 2010, 15:15–15:30, H23

Phase Stability in Magnetocaloric La(Fe,Si)₁₃ Ribbons — •Maria Krautz, Jian Liu, Julia Lyubina, Konstantin Skokov, Ludwig Schultz, and Oliver Gutfleisch — IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden

In the last decade several materials, exhibiting a giant magnetocaloric effect (MCE), have been studied. Magnetic refrigeration appears now as a viable alternative to conventional gas compression/expansion techniques. Some alloys with the NaZn₁₃-structure are of high interest, as they show a first-order phase transition in the vicinity of the Curie temperature, leading to a giant MCE. As the binary LaFe₁₃-phase does not exist, it has to be stabilised by adding a third element such as Al or Si. In order to remove the primary α-Fe and obtain nearly pure 1:13-phase from the as-cast alloy, a prolonged heat treatment taking up to several weeks is usually performed. The melt-spinning technique is proven to be very useful to synthesize various functional magnetic materials with a homogenous chemical composition and a refined microstructure. Here we applied this technique to the La-Fe-Si system. After a short time annealing of only a few hours, the 1:13-phase is established in the melt-spun ribbons. However, little knowledge about the pseudobinary phase diagram of La(Fe,Si)₁₃ is available so far. Therefore, melt-spun alloys with different Si contents were annealed at different temperatures. The structure was studied by XRD (Rietveld-refinement) and SEM and correlated with magnetic data. In view of application, the significant volume change of the 1:13-phase during the magnetic phase transition is analysed.