Berlin 2015 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 51: Magnetic Shape Memory Alloys (Joint Session with MM)

MA 51.4: Vortrag

Freitag, 20. März 2015, 10:15–10:30, H 0112

Effects of annealing on the martensitic transformation of Ni-based ferromagnetic shape memory Heusler alloys and nanoparticles — •Tina Fichtner, Changhai Wang, and Claudia Felser — Max Planck Institute for Chemical Physics of Solids, Dresden, Germany

We report on the effects of annealing on the martensitic phase transition in the Ni-based Heusler system: bulk Ni-Mn-Sn and Co-Ni-Ga nanoparticles. For the powdered Ni-Mn-Sn, structural and magnetic measurements reveal that re-annealing reduces the martensitic phase transformation. This might be associated with a release of internal stress in Ni-Mn-Sn compound during the annealing process. Whereas in the case of Co-Ni-Ga nanoparticles, a vice versa phenomenon is observed. The as-prepared Co-Ni-Ga nanoparticles do not show the martensitic phase transition, as revealed by temperature-dependent x-ray diffraction measurements. However, post-annealing followed by ice quenching is found to trigger the formation of the martensitic phase in Co-Ni-Ga nanoparticles. The occurrence of the martensitic transition is attributed to the modified phase structure and the introduced stress due to annealing.