Berlin 2024 – scientific programme

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DS: Fachverband Dünne Schichten

DS 8: Thin Film Properties II

DS 8.10: Talk

Wednesday, March 20, 2024, 12:15–12:30, A 060

Analysis of 3D check board pattern formation in NiCoMnAl shape memory alloys with alternating austenitic and martensitic layers — •Dario Stierl, Andreas Becker, Laila Bondzio, Inga Ennen, and Andreas Hütten — Universität Bielefeld

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. The thermal hysteresis could be reduced in NiCoMnAl thin films with alternating active transforming austenitic layers and martensitic intercalations. The stoichiometry of these two layers is chosen in such a way that their thermal hysteresis does not overlap. In addition, a 3D check board pattern becomes visible in HRTEM cross section images if the austenite active layers and martensite intercalations possess similar thicknesses.

In this contribution we aim for an improved understanding of the 3D check board pattern formation. Therefore, we varied the number of the alternating layers in one series and changed the ratio between the thicknesses of the two different layers in a different series. Furthermore, we analyzed the samples with temperature dependent XRD measurements. Additionally freestanding films were prepared and measured.

Keywords: NiCoMnAl; shape memory alloy; martensitic transformation