Magnetic characterization of intermetallic PrMn2Ge2-xSix compounds by AC susceptibility, x-ray diffraction and differential scanning calorimetry studies

X-ray powder diffraction, AC susceptibility and differential scanning calorimetry (DSC) studies were performed on the polycrystalline PrMn2Ge2-xSix (0 ≤ x ≤ 2) compounds. All compounds investigated crystallize in the body-centred tetragonal ThCr2Si2-type structure with the space group I4/mmm. Substitution of Si for Ge leads to a linear decrease of the lattice constants and the unit cell volume. The lattice constants and the unit cell volume obey Vegard's law. Samples in this alloy system exhibit a crossover from ferromagnetic ordering for PrMn2Ge2 to antiferromagnetic ordering for PrMn2Si2 as a function of Si concentration x. At low temperatures, the Pr sublattice also orders for x ≤ 0.4. The samples with x ≤1.3 are ferromagnetic and have spin reorientation temperatures just below the Curie temperature. In the cases of x = 1.2 and 1.3, re-entrant ferromagnetism is observed. The samples with x ≥1.6 are antiferromagnetic below the Neel temperature TN(Mn). By comparing our results to earlier neutron diffraction and Moessbauer studies, the x-T magnetic phase diagram has been constructed