Itinerant-electron theory of metamagnetism

Itinerant-electron theory of metamagnetism taking into account the effect of spin fluctuations is proposed on the Hubbard model within the static approximation in the functional integral formalism. It is possible to treat the metamagnetism of the system with large amplitudes of the moment and spin fluctuation. Effects of spin fluctuations and Stoner excitations on the temperature-dependence of paramagnetic susceptibility and the metamagnetic transition under external magnetic field are investigated numerically on a simple model (electronic) density of states. It is shown that both effects are quantitatively important in metamagnetism.