Yb Valence Fluctuations and Kondo-Like Behavior in the Yb1−Xscxco2zn20 System

In this study, we change the chemical pressure within YbCo 2 Zn 20 by substituting the radially smaller Sc for Yb (Yb 1− x Sc x Co 2 Zn 20 ) in order to investigate the relationship between pressure and the correlated electron ground state of Yb. We find that the behavior of Yb 1− x Sc x Co 2 Zn 20 is divided into two regimes, x ≤ 0.3 and x > 0.3. Resistivity ( ρ ( T )) measurements reveal not only a low-temperature upturn that can be described by a log T -dependence, consistent with the predictions of the single ion Kondo model, but also that the large and robust Kondo contribution to the resistivity observed in the range 0 ≤ x ≤ 0.3, becomes much weaker for 0.3 < x ≤ 1. We determine the Yb valence v Yb from X-ray powder diffraction (XRD) patterns at room temeprature and magnetization ( M ( T )) measurements and observe that v Yb decreases linearly from ∼ 3+ at x = 0 to ∼ 2.7+ at x = 0.3 before stabilizing back at ∼ 3+ for 0.3 < x ≤ 1. We analyze C ( T ) /T for Yb 1− x Sc x Co 2 Zn 20 and find signatures consistent with non-Fermi liquid (NFL) like behavior, suggesting a nearby quantum critical point (QCP). The Yb 1− x Sc x Co 2 Zn 20 system shows a confluence of phenomena typically found in 4 f electron systems including valence fluctuations, the Kondo effect, and heavy fermion behavior.