Archiviertes Physik-Kolloquium:

01. Dec. 2016, 16:15 Uhr, Gebäude NW1, Raum H3

Ferromagnetism of transition metals

Prof. Dr. Florian Gebhard, Marburg

In transition metals such as iron and nickel, the narrow 3d bands are partly filled. Their magnetic ground state is the consequence of the electron-electron interaction and of Fermi statistics. Since the electron-electron interaction between the 3d-electrons is not a weak perturbation, many-body approaches are essential for a quantitative description of transition metals and their magnetic ground states. My presentation consists of three parts. First, recalling the basic concepts, I introduce the Slater-Stoner weak-coupling picture for band magnetism and the Hund-Heisenberg strong-coupling picture for magnetic insulators. Second, I discuss Gutzwiller’s many-body ground state that interpolates between the Slater-Stoner and Hund-Heisenberg pictures. This class of variational wave functions can be evaluated in the limit of high dimensions without further approximations. The Gutzwiller approach combines with standard (Spin-)Density Functional Theory (DFT), the present-day implementation of the Slater-Stoner band magnetism concept. Third, I present results of the Gutzwiller-DFT for nickel and iron. For nickel, all of the DFT shortcomings regarding lattice spacing, magnetic moment, bulk modulus, and Fermi-surface topology are resolved in the Gutzwiller-DFT. For iron, the large quasi-particle masses at the Fermi energy remain unexplained.