Coexistence of non-Fermi liquid behavior and biquadratic exchange coupling in La-substituted CeGe: Nonlinear susceptibility and DFT+DMFT study

Studies connected with the investigations of "non-Fermi liquid" (NFL) systems continue to attract interest in the condensed-matter physics community. Understanding the anomalous physical properties exhibited by such systems and its related electronic structures is one of the central research topics in this area. In this context, Ce-based and Ce-site diluted (with nonmagnetic ions) compounds provide a fertile playground. Here, we present a detailed study of nonlinear DC susceptibility and combined density-functional theory plus dynamical mean-field theory (DFT+DMFT) on Ce0.24 La0.76 Ge. Theoretical investigation of 4f partial density of states, local susceptibility, and self-energy demonstrates the presence of NFL behavior which is associated with fluctuating local moments. Nonlinear DC susceptibility studies on this compound reveal that the transition from NFL state to the new phase is due to development of the biquadratic exchange coupling and it obeys the nonlinear susceptibility scaling. Under the application of magnetic fields, local moments interact spatially through conduction electrons resulting in magnetic fluctuations. Our studies point to the fact that the origin of the observed biquadratic exchange coupling is due to the spatial magnetic fluctuations.