La1-xCexB6 (x≤0.1): spin-polaron regime in dilute magnetic system

Abstract

Precision measurements of charge transport characteristics (resistivity, magnetoresistance, Hall and Seebeck coefficients) and magnetic susceptibility have been carried out on high-quality single-crystals of the so-called dilute Kondo system La1-xCexB6 (χ≤0.1) in a wide temperature range 1.8–300 K. It is shown that the low temperature magnetic contribution in resistivity obeys the power law Δρ∼T-α, which corresponds to the regime of weak localization of charge carriers with the critical exponent values α=0.47–0.49 for cerium concentrations χ≤ 0.1. Simultaneously an asymptotic behavior of Seebeck coefficient S∼ -lnT is found together with nearly constant and negative Hall coefficient RH(T) in these dilute magnetic systems. The results of comprehensive analysis contradict to the predictions of Kondo-impurity approach for this archetypal strongly correlated electron system in dilute impurity limit. An alternative interpretation of the properties of La1-xCexB6 is developed and based on spin-polaron approach, Pauli paramagnetism and the density of states renormalization effects at low temperatures.