Investigation of the crystal structure and magnetic properties of Nd_(1-x)Gd_xMn_2Si_2 compounds

摘要

X-ray powder diffraction and DC magnetization studies were performed on the polycrystalline Nd_(1-x)Gd_xMn_2Si_2 (0 <= x <= 1) compounds. Magnetic properties were examined between 5 and 700 K in applied fields up to 50 kOe. All compounds investigated crystallize in the ThCr_2Si_2-type structure with the space group I4/mmm. Substitution of Gd for Nd leads to a linear decrease in the lattice constants and the unit cell volume. In the X(T) curves above room temperature, all samples show a clear peak coinciding with the Neel temperature due to antiferromagnetic coupling of the ferromagnetic Mn layers. At low temperatures below about 60 K, the rare earth sublattice orders and also the antiferromagnetic coupling of the ferromagnetic Mn layers becomes ferromagnetic. The samples with x = 0.2 and 0.6 exhibit a spin reorientation phenomenon. In terms of the mean field two-sublattice model, the values of the intrasublattice coupling constant n_(11) and the intersublattice coupling constant n_(12) for the antiferromagnetic phase have been derived from the temperature dependence of the magnetic susceptibility.