ITINERANT ELECTRONS IN STRONG MAGNETIC-FIELDS - ONSET OF A METAMAGNETIC TRANSITION

We present a model of a magnetic-field-induced metamagnetic transition in an itinerant electron system. The effect of the applied magnetic field is twofold-a part which splits the spin degeneracy and the other which flips the spins and orders them as the field stength is increased. The spin-flip component of the applied field drives the system to nonlinearity, and the resulting relaxation processes are included phenomenologically. The phase transition from the low-field paramagnetic state to a high-field ferromagnetic state is shown as a function of spin splitting and the Coulomb correlation. For small spin splitting, the transition occurs via a metamagnetic phase at a lower held and a smaller value of Coulomb correlation compared to the situation when the spin splitting is large. We have shown that large paramagnetic susceptibility and strong Coulomb correlation favor a metamagnetic transition and nonlinearity. The predictions are in accord qualitatively with some of the systematics of the metamagnetic transition recently observed in some itinerant and heavy fermion systems.