MAGNETIC-STRUCTURES OF THE NEW TBFESI2-TYPE STRUCTURE GERMANIDES - RMNCU(0.5)GE(1.5) (R=LA, CE, PR)

The TbFeSi2-type RMnCu(0.5)Ge(1.5) compounds (R = La, Ce, Pr) have bee n studied by magnetization and neutron diffraction experiments. All th ree compounds behave antiferromagnetically below T-N approximate to 40 0 K (a behaviour not detected by magnetization measurements). The magn etic structures are characterized by antiferromagnetic (010) Mn planes stacked along [010]. The Mn moments are relatively large (mu(Mn) appr oximate to 3.0 mu(B) at 2 K). At low temperature, the Pr sublattice or ders antiferromagnetically below T-t approximate to 140 K (mu(Pr) = 1. 9 mu(B) at 2 K). The magnetic order of the Mn sublattice is discussed and compared with those observed in the isotypic RMnSi(2) silicides an d in the closely related RMnX and RMn(2)X(2) (X = Si, Ge) compounds.