Physical properties of the Kondo-lattice compound Yb₂Ir₃Ge₅

Abstract

We report sample preparation, structure, electrical resistivity, magnetic susceptibility, and heat capacity studies on the compound Yb₂Ir₃Ge₅. We find that this compound crystallizes in an orthorhombic structure with a space group Pmmn unlike the compound Ce₂Ir₃Ge₅ which crystallizes in the tetragonal Ibam (U₂Co₃Si₅-type) structure. Our resistivity measurements indicate that the compound Yb₂Ir₃Ge₅ behaves like a typical Kondo-lattice system with no ordering down to 0.4 K. However, a Curie-Weiss fit of the inverse magnetic susceptibility above 100 K gives an effective moment of 3.66µ_B which is considerably less than the theoretical value of 4.54µ_B for magnetic Yb³⁺ ions. The value of θ_P=−15.19K is also considerably higher indicating the presence of strong hybridization. An upturn in the low-temperature heat capacity gives an indication that the system may order magnetically just below the lowest temperature of our heat-capacity measurements (0.4 K). The structure contains two sites for Yb ions and the present investigation suggests that Yb may be trivalent in one site while it may be significantly lower (close to divalent) in the other.