Kondo-lattice behavior and multiple characteristic temperatures in CeIr₂Ge₂

Abstract

The results of electrical-resistivity ρ measurements (1.4-300 K) on the alloys, Ce_1-xLa_xIr₂Ge₂ (0≤ x ≤ 1), CeIr_2-x(Rh,Pt)_xGe₂ (x=0.2 and 0.4), and CeIr₂Ge_2-x(Si,Sn)_x (x=0.2 and 0.4), are reported in order to understand the Kondo effect in CeIr₂Ge₂. There is a significant decrease in ρ as the temperature is lowered from 100 to 4.2 K for x = 0.0. This feature disappears for a small replacement of Ce by La (x = 0.3), thereby resulting in a single-ion Kondo effect for higher values of x. This finding establishes that the temperature T_coh, characterizing the coherent scattering among the Kondo centers for x=0 is as large as about 100 K. The coherent scattering is not destroyed by small substitutions at the Ir or Ge site. The observed sensitivity of this coherence effect to a small disruption of Ce sublattice periodicity alone by La substitution is uncommon among trivalent Ce alloys. Such a large T_coh value enables us to emphasize the need to invoke three characteristic temperatures for nonmagnetic Kondo lattices.