Transport properties and magnetoresistance in CoNb1−xMnxSb half-Heusler alloys with a low temperature localization

The transport properties and magnetoresistance of half-Heusler CoNb1−xMnxSb (x=0.0–1.0x=0.0–1.0) alloys have been investigated between 2 and 300 K. In this temperature range, a metallic conductivity has been observed for the alloys with higher (x=1.0x=1.0) and lower (x=0.0–0.2)(x=0.0–0.2) Mn contents. However, the middle Mn content alloys (x=0.4–0.8)(x=0.4–0.8) exhibit non-metallic conductive behavior. Their temperature dependence of resistivity undergoes a Mott localization law ρ=ρ0exp(T0/T)pρ=ρ0exp(T0/T)p (p=1/4p=1/4) rather than a thermal excitation regime ρ=ρ0exp(Ea/kT)ρ=ρ0exp(Ea/kT) at low temperature (T<25K). The localization can be attributed to atomic and magnetic disorder. Resistivity peaks from 25 to 300 K were also observed for these alloys. Magnetotransport investigation reveals that these resistivity peaks result from localization effect as well as spin-disorder scattering.