Transport properties of R0.01La0.99B6 solid solutions

Abstract

We report the study of resistivity and transverse magnetoresistance of LaB6 and R0.01La0.99B6 diluted systems (R–Ce, Pr, Nd, Eu, Gd, and Ho) measured at temperatures between 1.8 K and 300 K in magnetic fields up to 82 kOe. Our data allow us to observe the influence of a wide class of impurities on the transport properties of LaB6 host material accompanied by various interesting anomalies including a crossover from positive (R–La, Pr, Nd, Eu, and Gd) to negative (R–Ce, Ho) regime of magnetoresistance below inversion points. The temperature dependences of zero-field resistivity are shown to be well described by a sum of (i) Debye term from rigid boron cages (ΘD ≈ 1160 K) and (ii) the contribution from quasilocal vibrations of La3+ ions (ΘE1 ≈ 154–156 К and ΘE2 ≈ 320–340 К). We register a low-T rise of resistivity for the materials containing R–Ce, Pr, Nd, and Ho centers. It is found that instead of logarithmic behavior ρ(T)~−lnT, predicted by Kondo model, the scattering on magnetic impurities follows to power law ρ(T)~T−α (α ≈ 0.2–0.49), which corresponds to the regime of weak localization of the charge carriers.