Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 26: Magnetic Shape Memory Alloys II
MA 26.7: Vortrag
Mittwoch, 25. März 2009, 16:15–16:30, HSZ 103
Influence of alloying Ni-Mn-Ga with cobalt on structural, mechanical, and magnetic properties — •Katharina Rolfs1,2, Markus Chmielus1,3, Peter Müllner3, Robert C. Wimpory1, Winfried Petry2, and Rainer Schneider1 — 1Helmholtz-Zentrum Berlin für Materialien und Energie, Glienicker Str.100, D-14109 Berlin, Germany — 2Technische Universität München, Lichtenbergstr. 1, D-85747 Garching, Germany — 3Department of Materials Science and Engineering, Boise State University, 1910 University Dr., Boise, Idaho 83725, USA
Magnetic Shape-Memory Alloys (MSMAs) can potentially substitute giant magnetostrictive materials as well as piezoelectrical ceramics in actuating devices due to their large magnetically induced strain. By alloying the most commonly studied MSMA Ni-Mn-Ga with 5 at-% Co, the martensite- and Curie-temperature was increased to values above 160°C. Two structures have been observed in Ni-Co-Mn-Ga single crystalline samples. Besides the non-modulated tetragonal structure, one of the common structures of Ni-Mn-Ga, a non-modulated orthorhombic structure, has been observed, which shows a cyclic permutation of all three crystallographic axes by applying a mechanical stress. The stress-strain analysis and the crystallographic characterization will be discussed here in detail. The giant magnetocaloric effect at the first order phase transition in Ni-Mn-Ga is well known. This effect is strongly influenced by alloying Ni-Mn-Ga with Co. Depending on the Mn-Ga-ratio the entropy change at the phase transition is still huge, however with an opposite sign. The results will be discussed here as well.