Local quantum fluctuations in kondo quasicrystal approximant Ag-In-(CexY1−x)

Abstract

The ternary alloy Ag-In-Ce is the only Ce-based quasicrystal approximant showing the heavy fermion feature. Here, we report the physical properties of Ag-In-(CexY1−x). As the Ce concentration x is diluted by the nonmagnetic element Y, the spin glass freezing temperature Tf is progressively suppressed. At T > Tf, the uniform magnetic susceptibility and electronic specific heat coefficient show χðT; xÞ-1 ¼ α½T ζ þ θe ζ ffðxÞ] (where α is a constant, ζ' 0.7, and θeff is an effective Weiss temperature) and CðT; xÞ=T ¼ β ln½T=T0ðxÞ] (where β is a constant and T0 is a characteristic temperature), respectively. Near the critical concentration xc where θeff vanishes, χ and C=T exhibit power-law and logarithmic divergence, respectively, as T → 0. We stress that α, ζ, and β are independent of x, indicating that the T ζ and ln T terms come from local fluctuations that are present everywhere in the x-T phase diagram, regardless of quantum critical point. We argue that the quantum critical behavior is driven by valence fluctuations.