Hall Effect in LaB<sub>6</sub> and NdB<sub>6</sub>

Abstract

To shed more light on the peculiarities of ground state formation in RB6 Hall effect in NdB6 and LaB6 has been investigated on the single crystals at temperatures 2K<T<300K in magnetic fields H < 80kOe. The Hall coefficient RH and resistivity ρ have been measured by the sample rotation technique in fixed magnetic field to be perpendicular to the axis of rotation (<110> for LaB6 and <100> for NdB6). A very similar temperature behavior of RH(T) with the step–like anomaly near T ~ 25K has been established for both magnetic NdB6 and diamagnetic LaB6 at intermediate temperatures T>10K. The temperature independent behaviour of Hall coefficient (RH(LaB6) ~ –3.6•10-4 cm3/C, RH(NdB6) ~ –3.7•10-4 cm3/C) observed in the interval 10K<T<20K allowed to estimate the reduced charge carriers’ concentration n/nR ≈ 1.21±0.03 (nR– the concentration of La (Nd) ions). The Hall mobility μH = RH(T)/ρ(T) estimated for LaB6 and NdB6 was shown to be well fitted by the power law μH ~ T-α where α(LaB6) ≈ 1.5, α(NdB6) ≈ 0.6 at the intermediate temperatures 50K<T<300K and α(LaB6) ≈ 3 in the range 20K<T<50K. The drastic decrease of both the Hall mobility μH and the exponent α is discussed in terms of the magnetic scattering enhancement of conduction electrons on the localized 4ƒ–states of Nd3+ ions.