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

Abstract

The 1-K phase transition in ${\mathrm{UCu}}_{5}$, showing up in specific-heat data within the antiferromagnetic state below ${\mathit{T}}_{\mathit{N}}$\ensuremath{\simeq}15 K, was investigated. Neither the average internal fields seen by the ${\mathrm{\ensuremath{\mu}}}^{+}$ 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 ``heavy'' electrons, associated with the weak magnetism, and the other associated with the ``conventional'' antiferromagnetic order.