Charge instabilities at the metamagnetic transition
  We investigate instabilities in the charge channel in the vicinity of (meta-)magnetic transitions of itinerant electron systems. Based on a weak coupling analysis we argue that in a one-band $t$-$t'$ Hubbard model near the van Hove filling and dominant ferromagnetic fluctuations it is difficult to account for a microscopic mechanism for a d-wave Pomeranchuk deformation of the Fermi surface. A similar deformation has been considered for the metamagnetic transition in Sr$_3$Ru$_2$O$_7$. As an alternative we discuss the possibility of charge inhomogeneity on the nano scale. This extends the analogy of the metamagnetic transition to a liquid-gas transition. 
Carsten Honerkamp