Anomalous behavior of the low-temperature spin disorder resistivity in PrH2+x compounds

Pure PrH2 dihydride presents an antiferromagnetic transition at 3.35 K; above TN, a decrease of the resistivity ρ(T) is observed which can be explained by a Kondo effect but also by crystal field effects if the first non magnetic excited state Γ1 situated very near to the magnetic Γ5 ground state. Magnetic ordering and the resistivity minimum disappear in PrH2+x compounds when x ≥ 0.08; this can be explained if there is an inversion of the Γ5 and Γ1 states or if there is a splitting of the triplet Γ5 state due to a tetragonal deformation of the lattice. Anomalous values of the low temperature slope dρ/dT seem to correlate with the occurrence of this cubic-tetragonal transformation of the host lattice. (author)