Abstract
We have studied the optical properties of the heavy-fermion compound UNiAl at frequencies between 100 GHz and 1 THz (3 and 35 cm), temperatures between 2 and 300 K, and magnetic fields up to 7 T. From the measured transmission and phase shift of radiation passing through a thin film of UNiAl, we have directly determined the frequency dependence of the real and imaginary parts of the optical conductivity (or permittivity, respectively). At low temperatures the anisotropy of the optical conductivity along the and axes is about 1.5. The frequency dependence of the real part of the optical conductivity shows a maximum at low temperatures, around 3 cm for the axis and around 4.5 cm for the axis. This feature is visible already at 30 K, much higher than the Néel temperature of 4.6 K, and it does not depend on external magnetic fields as high as 7 T. We conclude that this feature is independent of the antiferromagnetic order for UNiAl, and this might also be the case for UPdAl and UPt, where a similar maximum in the optical conductivity was observed previously [Dressel et al., Phys. Rev. Lett. 88, 186404 (2002)].
2 More- Received 13 April 2011
DOI:https://doi.org/10.1103/PhysRevB.84.035132
©2011 American Physical Society