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 – 1.0 ) 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 = 1.0 ) and lower ( x = 0.0 – 0.2 ) Mn contents. However, the middle Mn content alloys ( x = 0.4 – 0.8 ) exhibit non-metallic conductive behavior. Their temperature dependence of resistivity undergoes a Mott localization law ρ = ρ 0 exp ( T 0 / T ) p ( p = 1 / 4 ) rather than a thermal excitation regime ρ = ρ 0 exp ( E a / k T ) at low temperature ( T < 25 K ). 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.