NEUTRON-DIFFRACTION STUDIES OF THE CEFESI-TYPE CAMNSI AND CAMNGE COMPOUNDS

The magnetic properties of the tetragonal CeFeSi-type compounds CaMnSi and CaMnGe have been investigated by neutron diffraction. They order antiferromagnetically below T-N similar to 360 and 420 K respectively (this was not detected by macroscopic measurements). Below T-N, the tw o magnetic structures are characterized by a stacking of purely antife rromagnetic (001) planes with the Mn magnetic moments (similar to 3.3 mu(B)) along the c-axis in the case of CaMnSi and 30 degrees tilted fr om this axis in the case of CaMnGe. The results are compared to those of isotypic rare earth manganese silicides and germandes and to the cl osely related ThCr2Si2-type RMn(2)Si(2) and RMn(2)Ge(2) compounds.