Low temperature electrical resistivity investigations of non-Fermi liquid behavior in strongly correlated f-electron systems

The non-Fermi liquid (NFL) regimes of several strongly correlated f-electron systems are investigated by means of electrical resistivity measurements as a function of temperature and, in some cases, as a function of magnetic field, with the goals of characterizing the range of temperature, substituent concentration, and magnetic field over which NFL behavior persists and identifying the mechanism(s) responsible for the NFL behavior.; The Y1-xUxPd3, Sc1-x UxPd3, and U1-xThxPd 2Al3 systems are found to exhibit an unconventional Kondo effect with NFL behavior at low temperatures for various dilute concentrations of uranium. At low temperatures, the temperature dependence of the electrical resistivity of these systems can be described by a power law of the form rho( T) = rho(0)[1 - a(T/ T0)n] with 0.5 ≤ n ≤ 1.5, where T0 can often be identified with the single-ion Kondo temperature TK. These results suggest a single-ion mechanism may be responsible for the NFL behavior of these systems. Theoretical models for this behavior that may be relevant include the multichannel Kondo effect (of magnetic dipole or electric quadrupole origin) or the Kondo disorder model.; The electrical resistivity of the U0.9Th0.1Be 13 and U1-xYxPd2Al3 systems was also found to follow a power law temperature dependence with 0.9 ≤ n ≤ 1.5. However, the resistivity data of these samples were found to saturate at the lowest temperatures with a positive slope, in contrast to the behavior of the three systems described previously, and similar to the behavior found in several heavy fermion compounds. Some aspects of the behavior of the U0.9Th0.1Be13 system are reminiscent of the quadrupolar Kondo model. The fact that the non-Fermi liquid behavior of the U1-xYxPd2Al3 system occurs in close proximity to the yttrium concentration at which a spin-glass freezing temperature extrapolates to T = 0 K suggests that fluctuations of an order parameter above a second order magnetic phase transition may be responsible for the NFL behavior of this system.