Crystal structure and magnetic properties of Nd(Mn_1-xFe_x)₂Si₂ compounds

X-ray powder diffraction, resistivity and magnetization studies have been performed on polycrystalline Nd(Fe_xMn_{1 - x})₂Si₂ (0 ≤ x ≤ 1) compounds which crystallize in a ThCr₂Si₂-type structure with the space group I4/mmm. The field-cooled temperature dependence of the magnetization curves shows that, at low temperatures, NdFe₂Si₂ is antiferromagnetic, while the other compounds show ferromagnetic behaviour. The substitution of Fe for Mn leads to a decrease in lattice parameters a, c and unit-cell volume V. The Curie temperature of the compounds first increases, reaches a maximum around x=0.7, then decreases with Fe content. However, the saturation magnetization decreases monotonically with increasing Fe content. This Fe concentration dependent magnetization of Nd(Fe_xMn_1-x)₂Si₂ compounds can be well explained by taking into account the complex effect on magnetic properties due to the substitution of Mn by Fe. The temperature's square dependence on electrical resistivity indicates that the curve of Nd(Fe_0.6Mn_0.4)₂Si₂ has a quasi-linear character above its Curie temperature, which is typical of simple metals.