Anomalous electron transport Nd₂Fe₁₄B single crystals

In contrast to the case of pure Fe, the increase in resistivity of Nd₂Fe₁₄B at temperatures higher than half the Curie point is exceedingly small and the Curie point d rho /dT anomaly has the opposite sign. The results are related to the giant Invar effect observed in Nd₂Fe₁₄B. The persistence of this effect above the Curie point may lead to an apparent anomalous phonon resistivity slope in the paramagnetic phase. At low temperatures the behaviour of rho is dominated by the Nd³⁺ crystal field levels. A single model using realistic level splittings accounts satisfactorily for the observed behaviour.