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Regensburg 2004 – scientific programme

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MA: Magnetismus

MA 23: Hauptvortr
äge - Symposium Magnetic Shape Memory Alloys (zusammen mit M)

MA 23.3: Invited Talk

Thursday, March 11, 2004, 11:15–11:45, H23

The magnetic, structural and dynamical properties of the Heusler alloys — •Alexey Zayak and Peter Entel — Theoretische Tieftemperaturphysik, Universität Duisburg-Essen, 47048 Duisburg

We have performed first-principles calculations of a series of Heusler compounds. In particular, the ferromagnetic alloys Ni2MnGa and Ni2MnAl are of interest because of their shape-memory properties. The ab-initio methods allow an accurate description the cubic, tetragonal and orthorhombic as well as the long-range modulated structures. The latter were found to be critically important for the stability of the martensitic states allowing for c/a ratios smaller then 1. In addition we have calculated the phonon spectra. The high symmetry cubic structure L21 turned to be unstable at zero temperature, both for Ni2MnGa and Ni2MnAl, due to the transverse acoustic mode which softens with the wave vector close to 1/3[110](2π/2). The obtained results are analysed in terms of the electronic configuration and charge transfer.

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