Electrical conductivity of ThMn12- and Th2Zn17-type ternary intermetallic compounds in R-T-Al systems (R=Y, La, Ce, Gd, Tb; T=Mn, Fe)

Electrical resistivity measurements in the temperature range 1.5-300 K were performed for ThMn12 and Th2Zn17 structure type RMnxAl12-x and R2MnxAl17-x (R=Y, La, Ce, Gd, Tb; T=Mn, Fe) ternary intermetallic compounds. There is a correlation between the ordering of the crystal structure and the type of the electrical conductivity in R-Mn-Al ternaries. Hopping conductivity in terms of variable range hopping (VRH) occurs in RMnxAl12-x (structure type ThMn12) and R2MnxAl17-x (structure type Th2Zn17) aluminides with disordered or partially ordered crystal structure, both for magnetic and nonmagnetic rare earths. Only for the RMn4Al8 stoichiometry with an ordered distribution of atoms, the resistivity exhibits metallic-type behavior. The presence of magnetic Fe atoms suppresses hopping conductivity in R-Fe-Al ternaries, evidencing that the 3d-element has a predominant influence on electronic transport in R-T-Al intermetallics