X-ray studies of magnetic phase transitions in the intermetallic compoundsRMn2Ge2 (R=La, Sm, Gd, Nd, Tb, and Y)

The lattice parameters a and c of the tetragonal intermetallic compounds RM n2Ge2 (R=La, Sm, Gd, Nd, Tb, and Y) have been measured by x-ray diffraction in the temperature interval 10-800 K. Anomalies are observed in the temper ature dependence of a and c due to phase transitions from the paramagnetic to the magnetically ordered state in the Mn subsystem, transitions between various magnetically ordered phases due to a change in the magnitude and si gn of the Mn-Mn exchange interaction, and magnetic transitions caused by or dering of the rare-earth subsystem leading to a rearrangement of the magnet ic structure of the Mn subsystem. It is concluded that, along with the latt ice parameter a, the lattice parameter c also has an influence on the Mn-Mn exchange interaction. (C) 1999 American Institute of Physics. [S1063-7834( 99)02911-1].