Structure and magnetic properties of (Nd,Y)3(Fe,Co,Ti)29 compounds

A series of Co-substituted compounds with nominal stoichiometries Nd1−xYxFe27.7−yCoyTi1.3 (x=0.3-2.1, y=3,6) and Nd1.5Y1.5Fe27.7−yCoyTi1.3 (y=3,6,9,11) were prepared and their structures were analyzed with powder X-ray diffraction (XRD) and neutron diffraction (ND). All samples are found to crystallize mainly in the R3(Fe,Ti)29-type structure with monoclinic symmetry (space group A2/m). The lattice parameters a, b and c and the unit cell volume V decrease monotonically with the increase of Y or Co content. The Curie temperature Tc and the saturation magnetization Ms are both found to increase with increasing Co content. The results of Rietveld refinements of the neutron diffraction data show that the stabilizing Ti atoms are distributed over the Fe2, Fe3 and Fe6 sites, while the Co atoms mainly occupy those Fe sites not shared with Ti atoms, particularly Fe8 and Fe11 sites.