MAGNETIC FLUCTUATIONS IN HEAVY-FERMION METALS

Elastic and inelastic neutron scattering have been used to study the a ntiferromagnetic ordering and magnetic excitations of the U heavy-ferm ion superconductors UPd2Al3 and URu2Si2 above and below T-N. While bot h materials exhibit the coexistence of superconductivity and antiferro magnetic order, the nature of the antiferromagnetic order and magnetic fluctuations is qualitatively quite different. UPd2Al3 resembles a ra re earth magnetic system with coupling of the 4f electrons to the cond uction electrons manifested in a broadening of otherwise conventional spin wave excitations. This is in marked contrast to the unconventiona l antiferromagnetism found in URu2Si2.