CRYSTALLOGRAPHIC DATA AND MAGNETIC-PROPERTIES OF NEW RCOGE (R-EQUIVALENT-TO-LA-ND) COMPOUNDS FROM SUSCEPTIBILITY MEASUREMENTS AND NEUTRON-DIFFRACTION STUDY

Investigations made by powder X-ray diffraction, susceptibility measur ements and neutron diffraction experiments on new ternary germanides R CoGe (R=La-Nd) are reported. They crystallize in the well-known tetrag onal CeFeSi-type structure (space group P4/nmm). This is closely relat ed to the ThCr2Si2- and CrB-type structures and can be described as is olated ''ThCr2Si2 blocks'' (BaAl4 slab) connected via R-R contacts (Cr B slab). LaCoGe is a Pauli paramagnet, whereas CeCoGe and PrCoGe are C urie-Weiss paramagnets down to 1.6 K. NdCoGe orders antiferromagnetica lly below TN=8 K; its magnetic structure consists of ferromagnetic (00 1) Nd layers (with moments lying in the (001) plane) antiferromagnetic ally coupled along the c axis with the sequence + + - - (mu(Nd) = 2.62 (4) mu(B)). In all compounds, no local moment was detected on the coba lt site. The results are discussed and compared with those obtained on the closely related NdCo2Ge2, NdGe and isotypic RFeSi compounds.