Heavy fermions have a large number of low-lying excitations. Antiferromagnetic superexchange typically favors low-spin arrangements for the ground state. A magnetic field favors high-spin arrangements over low-spin arrangements. The transition from a low-spin ground state to a high-spin ground state, as a function of magnetic field, passes through a range where there is a peak in the many-body density of states. This range qualitatively describes the metamagnetic transition.

• Received 24 February 1992

DOI:https://doi.org/10.1103/PhysRevB.46.874