MAGNETISM OF (FE,CO)-BASED ALLOYS WITH THE LA6CO11GA3-TYPE

Alloys with the composition RE6 (Fe, Co)13X (RE = La, Pr, Nd, Sm; X = As, In, Sn, Sb, Tl, Pb, Bi) have been synthesized by the arc melting technique, followed by annealing at 873-1273 K for up to 170 hr in evacuated silica capsules. From room temperature X-ray powder diffraction analysis the alloys were found to crystallize with the ordered La6Co11Ga3, i.e., the Nd6Fe13Si type of structure. Precise atom parameters and interatomic distances have been derived from a single crystal X-ray refinement of Pr6Fe13Pb. The La6Co13X compounds exhibit ferromagnetism with a saturation moment of μS ∼ 1μB/cobalt atom. From the magnetic behavior of the iron-containing samples antiferromagnetic coupling of at least two magnetic sublattices is concluded to be present because of the strongly reduced magnetization values. While the 37Fe Mössbauer spectra are essentially unaffected by the specific element X, a modified shape of the spectra is observed if the rare earth element is changed. In the case of RE = Nd the spectra indicate an easy c-axis of magnetization in the whole range between room and liquid helium temperature; in the case of RE = Pr a spin reorientation is anticipated. © 1993 Academic Press, Inc.