Magnetic characterization of intermetallicPrMn2Ge2−xSix compounds by AC susceptibility, x-ray diffraction and differential scanning calorimetrystudies

Abstract

X-ray powder diffraction, AC susceptibility and differential scanningcalorimetry (DSC) studies were performed on the polycrystallinePrMn2Ge2−xSix () compounds. All compounds investigated crystallize in the body-centred tetragonalThCr2Si2-type structure withthe space group I4/mmm. Substitution of Si for Ge leads to a linear decrease of the lattice constants and the unitcell volume. The lattice constants and the unit cell volume obey Vegard’s law.Samples in this alloy system exhibit a crossover from ferromagnetic ordering forPrMn2Ge2 to antiferromagneticordering for PrMn2Si2 as a functionof Si concentration x. At low temperatures, the Pr sublattice also orders for . The samples with are ferromagnetic and have spin reorientation temperatures just below the Curie temperature. In thecases of x = 1.2 and 1.3, re-entrant ferromagnetism is observed. The samples with are antiferromagnetic below the Néel temperatureTN(Mn). By comparing our results to earlier neutron diffraction and Mössbauer studies, thex–T magnetic phase diagram has been constructed.