Magnetic Isotherm of Itinerant Electron Magnets – A New Approach to Itinerant Electron Metamagnetism

Theoretical development on the magnetic isotherm in itinerant electron ferromagnets is briefly reviewed in comparison with observed magnetization measurements. Itinerant electron metamagnetic transitions originate from the magnetization curve derived from the negative fourth expansion coefficient of the free energy in magnetization. In our view, however, it is difficult to expect the negative coefficient of the magnetic origin. We therefor propose a new mechanism of the metamagnetic transition, by taking an explicit account of volume dependence of the free energy, which is consistent with our spin fluctuation theory of magnetic isotherms.