Study of the 1-K phase transition in the heavy-electron compound UCu5 by muon spin resonance and neutron scattering

The 1-K phase transition in UCu5, showing up in specific-heat data within the antiferromagnetic state below TN 15 K, was investigated. Neither the average internal fields seen by the + nor the magnetic and nuclear Bragg reflections in the neutron-diffraction data reflect the phase transition while the muon relaxation rates increase drastically below 1.2 K. These results are interpreted in terms of some additional small-moment magnetic order or spin-density-wave phenomenon, implying the coexistence of two rather independent electronic subsystems, one involving eeheavyee electrons, associated with the weak magnetism, and the other associated with the eeconventionalee antiferromagnetic order.