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.