ThMn12-type magnetic ErFe7Al5 and non-magnetic YFe7Al5 studied by X-ray and neutron diffraction

Structure parameters and magnetic properties of ternary ErFe7Al5 and YFe7Al 5 intermetallics have been determined by X-ray and neutron diffraction. The compounds crystallize in the ThMn12-type structure of space group I4/mmm w ith 2a, 8f and 8i sites occupied by the rare earths (R), iron and aluminium , respectively, and remaining Fe and Al on 8j. Lattice constants and intera tomic distances are discussed in the context with results of previously inv estigated R(FexAl1-x)(12) compounds of lower iron concentrations. Around 32 0 K, ErFe7Al5 undergoes a magnetic phase transition into a ferrimagneticall y ordered state with antiparallel orientations of Er and Fe(8f) spins withi n the tetragonal basis plane. The moment values are 8.4(2) mu(B) and 2.9(3) mu(B) at 4.2 K per Er- and Fe-ion, respectively. In YFe7Al5, however, no l ong range magnetic order is observed. (C) 2000 Elsevier Science S.A. All ri ghts reserved.