NEUTRON-DIFFRACTION STUDY OF ND0.35LA0.65MN2SI2 - A SMMN2GE2-LIKE MAGNETIC-BEHAVIOR COMPOUND

Magnetization and neutron diffraction measurements on the ThCr2Si2-typ e structure Nd0.35La0.65Mn2Si2 compound are reported. This compound is characterized by re-entrant ferromagnetic behaviour, as observed in t he SmMn2Ge2 compound, with three characteristic magnetic transitions a t T-C = 295 K, T-t1 = 220 K (F --> AF) and T-t2 = 50 K (AF --> F). Neu tron diffraction study reveals the occurrence of an additional antifer romagnetic region (not detected by magnetometric measurements) charact erized by antiferromagnetic (001) Mn planes, between T-C = 295 K and T -N = 395 K. On the other hand, the occurrence of an in-plane antiferro magnetic Mn component (obviously correlated with a critical Mn-Mn intr alayer spacing value of similar to 2.87 Angstrom) over the whole order ed range leads us to strongly revise the ferromagnetic ordering previo usly proposed to take place on the Mn sublattice in such compounds, A new description of the thermal dependence of the Mn sublattice magneti c orderings within the RMn(2)X(2) (X = Si, Ge) compounds is proposed.