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MA: Magnetismus

MA 11: Magnetische Materialien

MA 11.6: Vortrag

Dienstag, 9. März 2004, 11:30–11:45, H22

Influence of nitrogen on the magnetic properties of LaFe_11.4Si_1.6 — •Aru Yan, Kalyan Mandal, Axel Handstein, Dieter Eckert, Konstantin Nenkov, Oliver Gutfleisch, and Karl-Hartmut Müller — Leibniz Institute of Solid State and Materials Research Dresden, POB 270116, 01171 Dresden

Recently, it was found that the intrinsic magnetic properties of La(Fe, M)₁₃ compounds (M = Al, Si) can be modified with interstitial H, C and N atoms, but the reported values of magnetic properties of the La(Fe, M)₁₃ interstitially modified compounds are much lower than those of the 2:17 and 1:12 interstitially modified compounds. In this work, LaFe_11.4Si_1.6N_x compounds have been prepared by nitrogen absorption and their magnetic properties have been investigated. It was found that the cubic NaZn₁₃-type structure of the Si containing compounds remains unchanged, while the lattice constant at room temperature is increased from 11.47 to 11.56 Å after nitrogen absorption at 973 K, leading to a large volume expansion of 2.4%. A drastic improvement of magnetic properties has been observed after the introduction of interstitial nitrogen. The Curie temperature is significantly increased from 200 K to 995 K and a high saturation magnetization of 93 emu/g is obtained. Further analysis revealed that the volume expansion plays a predominant role in improving the magnetic properties of La(Fe_xSi_1−x)₁₃N_x. In particular, the significant increase of Curie temperature in LaFe_11.4Si_1.6N_x can be attributed to the enhancement of the exchange interaction by the nitrogen absorption.