Thermal conductivity, thermoelectric power and Mössbauer investigations on atiferromagnetic CeFe_1.7Ir_0.3Al₁₀

CeFe₂Al₁₀ is known to exhibit a Kondo semiconducting behavior without any signature of long range magnetic ordering. A partial Ir substitution for Fe in CeFe₂Al₁₀ is found to drive the system towards long range magnetic ordering, and a 15% Ir substitution is found to result in an antiferromagnetically ordered state below 3.1(2) K in CeFe_1.7Ir_0.3Al₁₀. We present the results of the electrical resistivity ρ, thermal conductivity κ and thermoelectric power S measurements as a function of temperature T, and ⁵⁷Fe Mössbauer spectroscopy on polycrystalline CeFe_1.7Ir_0.3Al₁₀. The ρ(T) exhibits Kondo lattice behavior and presents evidence for the formation of a superzone gap in antiferromagnetic state. We estimate Kondo temperature T_K≈18 K. The κ(T) does not show any anomaly and reflects a phonon dominated thermal transport. The Lorenz number L(T)=κ(T)ρ(T)/T is found to be much larger than the theoretical Sommerfeld value L₀ which also reflects a phonon dominance. The S(T) exhibits a minimum at low T (S_min≈−2.3μV/K, T_Smin≈30 K) and a maximum at high T (S_max≈5.4μV/K, T_Smax≈225 K). The S(T) data are described by a two-band model with contributions from two Lorentzian shaped f-bands. From the analysis of S(T), we infer that while one of the contributing f-band lies 22 K below the Fermi energy E_F, the other one is at 190 K above E_F. The ⁵⁷Fe Mössbauer spectra collected in zero field do not show clear evidence of magnetic ordering, however, the Mössbauer measurements in external fields support an antiferromagnetic ordering in CeFe_1.7Ir_0.3Al₁₀.