ITINERANT-ELECTRON THEORY OF METAMAGNETISM

Itinerant-electron theory of metamagnetism taking into account the eff ect of spin fluctuations is proposed on the Hubbard model within the s tatic approximation in the functional integral formalism. It is possib le to treat the metamagnetism of the system with large amplitudes of t he moment and spin fluctuation. Effects of spin fluctuations and Stone r excitations on the temperature-dependence of paramagnetic susceptibi lity and the metamagnetic transition under external magnetic field are investigated numerically on a simple model (electronic) density of st ates. It is shown that both effects are quantitatively important in me tamagnetism.