Dresden 2011 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 41: Topical Session Diffussionless Transformations II

MM 41.4: Talk

Thursday, March 17, 2011, 17:00–17:15, IFW D

First-principles investigation of the magnetic shape memory system Co-Ni-Ga — •Mario Siewert, Markus E. Gruner, Antje Dannenberg, and Peter Entel — Faculty of Physics and CeNIDE, University of Duisburg-Essen, 47048 Duisburg, Germany

The magnetic shape memory (MSM) system Ni-Mn-Ga still has limited applications because the operating temperatures are not suitable for many practical devices. Hence, the search for new ferromagnetic shape memory compounds is not only of scientific but also of industrial importance. One approach to find new MSM alloys are Heusler compounds based on Co. Here, we present first-principles results for the Co-Ni-Ga system. In particular, the structural, electronic and dynamic properties of stoichiometric Co₂NiGa and off-stoichiometric compositions have been investigated using density functional theory. Our results reveal that there is a competition between tetragonal distorted and bcc-like structures. In addition, a competition between different structural orderings, namely the regular Heusler structure and the so called inverse Heusler structure, occurs. In advance, no phonon softening along the [110] direction is found for Co-Ni-Ga in agreement with neutron scattering measurements. This is supported by the electronic structure which reveals no sign of Fermi surface nesting.