Magnetic properties of the Hubbard model on the fcc lattice

As a possible model for ferromagnetism, we study the magnetic properties of the Hubbard model on an fcc lattice. Near-neighbor and next-near-neighbor hopping parameters are included to examine the effect of band structure. We use exact diagonalization and the Constraint Path Monte Carlo (CPMC) \footnote{S.~Zhang, J.~Carlson, and J.~Gubernatis, Phys.~Rev.~B {\bf 55}, 7464 (1997); C.-C.~Chang and S.~Zhang, Phys.~Rev.~B {\bf 78}, 165101 (2008).} methods. Several methodological improvements in CPMC, for example the release of the constraint, will be discussed. We present benchmark quality results on the paramagnetic ground state and partially polarized states, as a function of interaction strength. A magnetic phase diagram is obtained from our many-body calculations, and comparison will be made with results from Dynamical Mean Field theory \footnote{ M.~Ulmke, The Eur. Phys. J.~B.~{\bf 1}, 301 (1998) }.