A magnetic study of LaMn2-xCoxSi2 silicides

X-ray diffraction (XRD) and AC magnetic susceptibility measurements have been performed on polycrystalline LaMn2-xCoxSi2 (0.0≤x≤1.0) silicides to investigate how the ferromagnetic interactions in LaMn2Si2 are affected by Co substitution. All the compounds crystallize in the naturally layered ThCr2Si2-type structure with the space group I4/mmm. Substitution of Co for Mn leads to a linear decrease in the lattice constants and also the unit cell volume. For the samples with x≤0.4, a ferromagnetic ordering within the Mn sublattice occurs below the Curie temperature TC(Mn). TC(Mn) decreases with the cobalt content from 310 K (x=0) to 186 K (x=0.4). For the samples with x≤0.3, the temperature dependence of the AC susceptibility shows a distinct feature below TC(Mn). These samples have a mixed state composed of ferromagnetic and anti-ferromagnetic phases. The samples with x=0.6 and have the Neel temperature associated with anti-ferromagnetic behavior. The results are collected in the partial magnetic phase diagram