Atomic correlations in itinerant ferromagnets:: Quasi-particle bands of nickel

The Gutzwiller theory is demonstrated to resolve most of the long-standing discrepancies between experiment and theory on the quasi-particle bands of ferromagnetic nickel. This is confirmed by new angle-resolved photoelectron spectroscopy data along various high-symmetry lines of the bulk Brillouin zone obtained under full control of the three-dimensional momentum. Our findings support he view of itinerant ferromagnetism as a consequence of atomic correlations.