Site occupancy and lattice changes on nitrogenation in Nd3Fe29−<i>x</i>Ti<i>x</i>N<i>y</i>

Abstract

The structure of Nd3Fe29−xTixNy has been determined by neutron diffraction and compared with the unnitrided parent. Nitrogen is found in the two large octahedral interstitial sites with four Fe and two rare-earth neighbors, leading to a concentration of y=4. The lattice expands by 6.4% (ΔV/V) but the expansion is anisotropic in the axes. Although most of the Fe–Fe bond lengths expand, a few show significant contraction, most notably the Fe3–Fe3 dumbbell, which has an extremely short 2.18 Å length.