NEUTRON-DIFFRACTION STUDY OF THE TBMNGE COMPOUND

The magnetic properties of the new TiNiSi-type TbMnGe compound have be en studied by magnetization measurements and neutron diffraction. Betw een T-N = 510 K and T-t1 approximate to 200 K the magnetic structure i s collinear antiferromagnetic, with both Tb and Mn moments aligned alo ng [100]. Below T-t1, a hat spiral structure characterized by a (q(r), 0,0) wavevector occurs. The Mn and Tb moments almost lie in the (001) plane. Below T-t2 approximate to 50 K, the component of the wavevector q(x) is equal to 1/4 and the magnetic structure becomes commensurate. At 2 K, the values of the magnetic moments are: mu(Mn) = 3.53(11) mu( B) and mu(Tb) = 9.16(9) mu(B). In the whole ordered range, the magneti c structure is characterized by antiferromagnetic Mn-Mn zigzag chains aligned along [010].