Metamagnetism and Fermi surface in the Anderson lattice model

We investigate magnetization as a function of external magnetic field H in the U-infinite Anderson lattice model within the leading-order approximation in the 1/N-expansion. At T = 0, at H = H-M where the Zeeman energy is equal to a certain characteristic energy of the system, the magnetization curve has a kink and the differential susceptibility dM/dH shows a jump. At finite temperature, dM/dH shows a peak around H-M. Its maximum value increases with decreasing T and saturates to a finite value at T --> 0. When H < H-M, the f and conduction electrons form renormalized bands with a large Fermi surface determined by the Luttinger sum On the other hand, when H > H-M, the bands reform such that they are free from the Luttinger sum rule, eventually leading to a small Fermi surface at H >> H-M. These results are consistent with the metamagnetic properties observed in the heavy fermion compound CeRu2Si2.