Magnetic and Charge Correlations of the 2-dimensional $t-t'-U$ Hubbard   model
  Using a spin-rotation invariant six-slave boson representation, we study the square lattice Hubbard model with nearest-neighbor hopping $t$ and next-nearest neighbor hopping $t'$. We discuss the influence of $t'$ on the charge and magnetic properties. In the hole-doped domain, we find that a negative $t'$ strongly favors itinerant ferromagnetism over any incommensurate phase, especially in the strong coupling regime. For positive $t'$ magnetic fluctuations are suppressed. A tight connection between frustrated charge dynamics and large magnetic fluctuations is pointed out. A clear tendency towards striped charge ordering is found in the regime of large positive $t'$. 
Raymond Fr\'esard and Walter Zimmermann