Metamagnetic transition in UPt3 studied by high-field magnetization and de Haas-van Alphen experiments

A heavy fermion superconductor UPt3 exhibits the metamagnetic transition at about 20 T. High-held magnetization experiments reveal that this transition persists up to about 30 K, which is close to the characteristic temperature T-chi max (similar or equal to 20 K) where the magnetic susceptibility has a maximum in the temperature dependence. Below T-chi max, the magnitude of magnetic fluctuations increases and forms the heavy fermion state at low temperatures. This is reflected in the growth of the cyclotron effective mass. The mass in the main band 37-electron Fermi surface, which was determined by the de Haas-van Alphen experiments, is strongly enhanced with increasing the held, from 63m(0) at 12.5 T to 86m(0) at Is T. This is consistent with the field dependence of the electronic specific heat coefficient. [S0163-1829(99)04534-8].