  Theoretical studies of the metamagnetism and anomalous phase of Sr3Ru2O7 have
focused on the role of van Hove singularities, although much experimental
evidence points towards quantum criticality having a large effect. We
investigate the magnetic and thermodynamic properties of systems where magnetic
field tunes through such a peak in the electronic density of states. We study
the generic case of a van Hove singularity in 2D. We see that in combination
with the requirement of number conservation and interaction effects the peak in
the density of states produces several interesting phenomena including raising
the critical field of the transition above naive estimates, altering the
relationship between temperature and field scales and creating a distinctive
double-peak structure in the electronic specific heat. We show that this
apparent non-Fermi liquid behaviour can be caused at mean-field level by a peak
in the density of states.
