Magnetic phase transitions in LaMn2−xFexSi2 silicides

The magnetic phase transitions in LaMn2−xFexSi2 (0.0≤x≤1.0) silicides were studied by X-ray diffraction, differential scanning calorimetry techniques and AC magnetic susceptibility measurements. All compounds crystallize in the ThCr2Si2-type structure with the space group I4/mmm. The lattice constants and the unit cell volume obey Vegardʹs law. For the samples with x≤0.4, the ferromagnetic interactions within the Mn sublattice occurs below the Curie temperature (TC(Mn)). The Curie temperature was depressed linearly by the substitution of Fe for Mn. The temperature dependence of the AC susceptibility shows a distinct feature for the samples with x≤0.3 below TC(Mn). These samples have a mixed state composed of ferromagnetic and anti-ferromagnetic phases. The samples with x≧0.6 have the Néel temperature below the room temperature, while the other samples are anti-ferromagnetic above the room temperature. The results lead to the construction of the partial magnetic phase diagram.