Neutron-powder-diffraction study of ${\mathrm{YFe}}_{12\mathrm{-}\mathit{x}}$${\mathrm{Mo}}_{\mathit{x}}$ and ${\mathrm{YFe}}_{12\mathrm{-}\mathit{x}}$${\mathrm{Mo}}_{\mathit{x}}$${\mathrm{N}}_{1.0}$ (x=1 and 3)

${\mathrm{YFe}}_{12\mathrm{-}\mathit{x}}$ ${\mathrm{Mo}}_{\mathit{x}}$ (x=1 and 3) and full-charged nitrides were prepared. Neutron-powder-diffraction experiments were performed at 10 K and room temperature on both the host compounds and their nitrides. The Rietveld technique was used for data analysis. Mo was found to reside mainly on the 8i site in the tetragonal ${\mathrm{ThMn}}_{12}$ structure (space group I4/mmm), with a small fraction on the 8f site. The nitrides retain the crystallographic symmetry of the host compounds. Nitrogen atoms are located on the 2b site with nearly 100% occupancy. The nitrogenation-induced modification of the rare-earth environment and in turn the magnetocrystalline anisotropy properties are discussed. The refined moments are comparable with those obtained by magnetization measurement.