Spin Fluctuations in the Heavy Fermion Superconductor UPd_<b>2</b>Al_<b>3</b>Studied by Neutron Inelastic Scattering

Abstract

We have found that there are two contributions to the dynamical response in UPd 2 Al 3 . The first is a heavily damped spin-wave, which has been observed previously. It shows no appreciable change on warming through T c , but softens and becomes overdamped as T approaches T N . The second is a quasielastic-like component that exists in the antiferromagnetically ordered state and is strongly localized around the ordered wavevector. As a function of temperature this component exhibits a minimum at the superconducting transition temperature T c , and increases strongly below T c . Its width in the momentum space at T = 0.5 K corresponds to a correlation length of ∼50 Å, which is close to the superconducting coherence length of ∼85 Å.