In this work, alloys of Nd(Fe1-xCox)10.5M1.5 (M=Mo and V) were prepared via arc melting and heat treatment. The nitrides of these alloys were synthesized using a gas-solid state reaction method. The influence of Co substitution for Fe in NdFe10.5Mo1.5 and NdFe10.5V1.5 alloys and their nitrides were investigated. It was found that the lattice parameters a, c, and unit cell volume V decrease with increasing Co content x for Nd(Fe1-xCox)10.5Mo1.5. As compared to their parent alloys, the lattice parameters and unit cells volume increase after nitrogenation, which gives rise to higher Curie temperature, magnetization and magnetocrystalline anisotropy field for nitrides. A small amount of Co substitution for Fe (x≤0.3) can enhance the magnetic properties including Curie temperature, saturation magnetization and magnetocrystalline anisotropy field of the alloys and their nitrides, while higher concentration of Co (x>0.3) will deteriorates these magnetic properties, especially for the nitrides, due to the modification of the band structure by Co atom. As a result, Nd(Fe1-xCox)10.5Mo1.5Ny and Nd(Fe1-xCox)10.5V1.5Ny with x≤0.2 become promising candidates for permanent magnet applications. A coercivity of 4.6 kOe and maximum energy product BHmax of 20 MGOe were achieved for NdFe9.45Co1.05Mo1.5Nx.
