Berlin 2018 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 52: Poster II

MA 52.30: Poster

Donnerstag, 15. März 2018, 15:00–18:00, Poster C

Influence of martensite intercalations on the thermal hysteresis in NiMn-based magnetic shape memory alloys — •Andreas Becker, Jan Peterhanwahr, Joris Swager, and Andreas Hütten — Bielefeld University, 33615 Bielefeld, Center for Spinelectronic and Materials

NiMnX (X=Al,Ga,Sn,In) magnetic shape memory Heusler alloys are considered as promising materials for magnetocaloric cooling applications due to their magnetoelastic coupling near room temperature[1]. However most of them show a very large thermal hysteresis, which can span over several hundreds of Kelvin, limiting their potential in future applications. Therefore efficient mechanisms to change the martensitic transformation behavior have to be found.

Our research showed that rigid substrates increase hysteresis width and residual austenite in NiCoMnAl thin films[2]. We concluded that thin martensite intercalations in those films should be the best available substrate for transforming films. Our aim is to reduce the thermal hysteresis in off-stoichiometric NiCoMnAl thin films, grown by sputter deposition, by preparing multilayer systems, which consist of alternatively grown martensite intercalations and active transforming layers. Stoichiometry of the layers is chosen in such a way that the martensite transformations do not overlap. The phase transition of the active layer is investigated by temperature dependent magnetic, electrical transport and x-ray diffraction measurements.

[1] Liu et al., Nature Materials 11, 7 (2012)

[2] M. Wodniok et al., AIP Advances 7, 056428 (2017)