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MA: Fachverband Magnetismus

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

MA 51.10: Talk

Friday, March 20, 2015, 11:45–12:00, H 0112

Structure and Giant Inverse Magnetocaloric Effect of Epitaxial Ni-Co-Mn-Al Films — •Niclas Teichert¹, Daniel Kucza¹, Oguz Yildirim^2,3, Ilker Dincer⁴, Anna Behler⁵, Lars Helmich¹, Alexander Boehnke¹, Anja Waske⁵, Yalcin Elerman⁴, and Andreas Hütten¹ — ¹Center for Spinelectronic Materials and Devices, Physics Department, Bielefeld University, Germany — ²Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf e.V., Germany — ³Dresden University of Technology, Germany — ⁴Ankara University, Department of Engineering Physics, Faculty of Engineering, Turkey — ⁵IFW Dresden, Institute for Complex Materials, Germany

The structural, magnetic, and magnetocaloric properties of epitaxial Ni-Co-Mn-Al thin films with different compositions have been studied. The films were deposited on MgO(001) substrates by co-sputtering on heated substrates. All films show a martensitic transition where the transition temperatures are strongly dependent on the composition. The structure of the martensite phase is shown to be 14M. The metamagnetic martensitic transition occurs from a strong ferromagnetic austenite to a weak magnetic martensite. The structural properties of the films were investigated by atomic force microscopy and temperature dependent X-ray diffraction. Magnetic and magnetocaloric properties were analyzed using temperature dependent and isothermal magnetization measurements. We find that Ni₄₁Co_10.4Mn_34.8Al_13.8 films show giant inverse magnetocaloric effects with magnetic entropy change of 5.8 J kg⁻¹K⁻¹ for µ₀ Δ H=1 T.