Neutron diffraction study on PrMn2−xFexGe2 and general magnetic phase diagram for RMn2−xFexGe2 (R: La-Sm)

We have investigated the magnetic structures and phase transitions of PrMn2−xFexGe2 (0 ≤ x ≤ 1) by the temperature dependence of weak-field magnetization and powder neutron diffraction. For the x = 0.6 sample, a typical SmMn2Ge2-like magnetic behavior is observed. The magnetic structures of the samples with x = 0.6, 0.8 and 1 have been determined between 1.5 and 305 K. Above TCinter (x = 0.6) and TNinter (x = 0.8 and 1) up to TNinter, these samples exhibit an intralayer antiferromagnetic structure in (0 0 1) Mn planes. For x = 0.6 sample, the magnetic structure is canted ferromagnetic along the c-axis between TNinter and TCinter and below TCPr. For the samples with x = 0.8 and 1, the magnetic structure is canted antiferromagnetic along the c-axis below TNinter. Pr moments order ferromagnetically along the c-axis for the x = 0.6 sample below TCPr. The results are summarized in the PrMn2−xFexGe2 magnetic phase diagram. The general magnetic phase diagram for RMn2−xFexGe2 (R: La, Ce, Pr, Nd and Sm) is also constructed from previous and present works. For these compounds, the magnetic phase transition from ferromagnetic to antiferromagnetic occurs at different intralayer Mn-Mn distances for each system. These critical distances are larger than the corresponding threshold value dMn-Mna=2.87Å for the ternary end-member RMn2X2 compounds.