Berlin 2005 – wissenschaftliches Programm

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MA: Magnetismus

MA 29: Magnetische Materialien

MA 29.8: Vortrag

Dienstag, 8. März 2005, 17:00–17:15, TU A060

Melt-spun LaFe13-xSix ribbons with large magnetic entropy change — •Aru Yan, Karl-Hartmut Müller, and Oliver Gutfleisch — Leibniz Institute of Solid State and Materials Research Dresden, Institute of Metallic Materials, P.O. Box 270016, D-01171 Dresden, Germany

LaFe13-xSix (X=1 1.8) compounds were prepared by melt-spinning and their structure and magnetic entropy change were investigated. The 1:13 phase with cubic NaZn13-type structure is obtained by a very short time annealing (1000-1050^∘C/1h) in melt-spun-type materials, which, in contrast, requires a very long time annealing at high temperature to develop in the bulk alloy. More importantly, a very large value of magnetic entropy change, 31 J/kg K, was obtained in LaFe11.8Si1.2 ribbons at 201 K under 5 T, which is much higher than that reported in the bulk alloys in this temperature range (LaFe11.44Si1.56,  23 J/kg K at 195 K). Further analysis confirms the occurrence of a typical first-order field-induced transition and a more homogenous element distribution resulting from the very high cooling rate in the LaFe11.8Si1.2 ribbons. With increasing Si concentration, the Curie temperatures are increased, while the maximum magnetic entropy changes are decreased due to weakening or disappearance of the first-order magnetic phase transition. The large value of magnetic entropy change and much reduced annealing programme make the melt-spun-type materials more appropriate for magnetic refrigerant applications, compared with conventional bulk alloys.