Regensburg 2010 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
MA: Fachverband Magnetismus
MA 8: Magnetic Shape Memory Alloys
MA 8.1: Vortrag
Montag, 22. März 2010, 15:15–15:30, H22
Lattice dynamics and static displacements in Fe-based magnetic shape memory alloys — •Markus E. Gruner and Peter Entel — Faculty of Physics and Center for Nanointegration, CeNIDE, University of Duisburg-Essen, 47048 Duisburg
Within the framework of density functional theory, we provide a comparison between stoichiometrically ordered Fe3Pt and disordered Fe-Pd magnetic shape memory alloys. We compare the analytic modelling of disorder within the coherent potential approximation (CPA) referring to the ideal lattice positions with an explicit description by supercell calculations allowing for the relaxation of the atomic positions. The calculations demonstrate that static displacements provide an important contribution to the variation of the total energy along the Bain path and are thus essential for the correct prediction of the ground state lattice structure. Distinct static relaxations are also present in all L12 ordered Fe-rich alloys with Ni-group elements, which can be described by an orthorhombic distortion of the Fe-octahedra encaged by the Ni-group sublattice. These manifest in a complete softening in the phonon dispersion at the M-point which we relate to nesting features of the Fermi surface.