Role of band structure in the thermodynamic properties of itinerant metamagnets

It is known that itinerant metamagnetic transitions can be driven by features in the electronic density of states. We study the signatures of these transitions in the entropy and specific heat for a variety of different cases, identifying the key features which differ from naive expectations, such as enhanced critical fields and non-Fermi-liquid temperature dependencies. We begin with the generic case of a logarithmically divergent density of states, as caused by a two-dimensional van Hove singularity. We then study a specific model for the band structure of Sr3Ru2O7, a material with a well-studied metamagnetic transition and quantum critical endpoint. We consider how far the behavior of the system can be explained by the density of states rather than quantum fluctuations, and the distinctive features of this mechanism. One of the characteristic features of Sr3Ru2O7 is an unusual phase with a higher entropy than its surroundings, and we consider how this may arise in the context of a density-of-states picture and find that we can reproduce the thermodynamic behavior and first-order phase transitions.