Lattice disorder in strongly correlated lanthanide and actinide intermetallics

Lanthanide and actinide intermetallic compounds display a wide range of cor related-electron behavior, including ferromagnetism, antiferromagnetism, no nmagnetic (Kondo) ground states, and so-called 'non-Fermi liquid' (NFL) beh avior. The interaction between f electrons and the conduction band is a dom inant factor in determining the ground state of a given system. However, la ttice disorder can create a distribution of interactions, generating unusua l physical properties. These properties may include NFL behavior in many ma terials. In addition, lattice disorder can cause deviations from standard K ondo behavior that is less severe than NFL behavior. A review of the lattic e disorder mechanism within a tight-binding model is presented, along with measurements of the YbBCu4 and UPdxCu5-x systems, demonstrating the applica bility of the model. These measurements indicate that while the YbBCu4 syst em appears to be well ordered, both site interchange and continuous bond-le ngth disorder occur in the UPdxCu5-x series. Nevertheless, the measured bon d-length disorder in UPdCu4 does not appear to be enough to explain the NFL properties simply with the Kondo disorder model.