STRUCTURE AND MAGNETIC PHASE TRANSITIONS OF THE NOVEL COMPOUND TbGe_3

摘要

We have studied the crystallographic and magnetic properties of the novel antiferromagnetic(afmg) compound TbGe3 by means of neutron diffraction (TN=40K). TbGe3 adopts the structure type reported earlier for DyGe3. A collinear afmg structure was observed by neutron diffraction in the range below 23K requesting a sixfold cell enlargement (2a,b,3c) and a fourfold splitting of the atomic positions. The magnetic structure may be described by a space group Pbmma (Sh51 299) or as a modulated structure with a five dimensional superspace group. In the range between 23 K and Tn the magnetic structure becomes incommensurate with the crystal lattice in both the a and the c directions and can be described as superposition of the Fourier coefficients associated with the wave vectors q1=(±qx 0,0) and q2=(±clxi0,±qz). This arrangement may be described by a superspace group of higher dimensions.