Dresden 2014 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 38: Magnetic Materials II

MA 38.5: Vortrag

Donnerstag, 3. April 2014, 10:45–11:00, HSZ 403

Epitaxial Ni-Mn-Ga-Co films for magnetocaloric application — •Anett Diestel^{1, 2}, Robert Niemann¹, Sebastian Fähler^{1, 3}, and Ludwig Schultz^{1, 2} — ¹IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, 01171 Dresden, Germany — ²Technische Universität Dresden, Institute of Materials Science, 01062 Dresden, Germany — ³Technische Universität Chemnitz, Institute of Physics, 09126 Chemnitz, Germany

The Heusler alloys Ni-Mn-X-Co (X = Ga, In, Sn, Sb) exhibit an inverse magnetocaloric effect (MCE) due to a field-induced martensitic transformation between austenite and modulated martensite which is accompanied by a large change of magnetization. The transformation temperatures sensitively depend on composition and chemical order so room temperature solid state refrigeration becomes feasible. For Ni-Mn-Ga-Co bulk an inverse MCE is known in comparison to the direct MCE of Ni-Mn-Ga. We prepared epitaxial Ni-Mn-Ga-Co films by magnetron sputter deposition on single crystalline MgO(100) substrates. Due to the high surface-to-volume fraction of thin films a fast heat exchange is possible and a higher cooling power can be achieved using less material. We proved epitaxial growth and the reversible field induced transformation from austenite to modulated martensite with a high change of magnetization. We also show the strong influence of deposition parameter and chemical composition on film growth, transformation temperatures and chemical order which influence the shape of magnetic hysteresis. This work is supported by DFG through SPP 1599 www.FerroicCooling.de.