NEUTRON-DIFFRACTION AND MAGNETIC STUDIES OF ND2FE17-X-ZALXSIZ

The Al and Si double-substituted 2:17 phase, Nd2Fe 17-x-zAlxSiz, was prepared and analyzed using neutron powder diffraction and SQUID magnetization measurements. Rietveld analysis of the neutron diffraction data indicates that the lattice parameters are close to a linear combination of the corresponding single-substitution compounds. The unit cell could be expanded or contracted, depending on the Al/Si ratio. The aluminum and silicon fractional occupancy on the different crystallographic sites in the double-substitution compounds are related to those of single-substitution compounds. The SQUID measurements show that all samples in this study have Curie points higher than that of the unsubstituted compound. For a Si/Al ratio of 2:1, the Curie point, 492 K, was found at a total substituent content less than in the singly substituted Si compound with the same Tc.