Frustration and two-dimensional spin ordering in TbRu2Si2, TbRu2Ge2 and DyRu2Si2

Long-period magnetic modulations in low-field-induced phases of TbRu2Ge2 at low temperatures

“…In the present case, therefore, the observed weak spots mentioned above would be a residue of the two-dimensional modulation of phase II and the spin modulation of phase I 0 would be onedimensional. On the other hand, for the pattern of phase III, magnetic satellites appear clearly not only on highsymmetry lines but also on low-symmetry lines like ðAE 4 17 k 0Þ, ð1 AE 4 17 k 0Þ and ðh 1 AE 4 17 0Þ, similar to the case of the zero-field phase II [5], indicating that the magnetic modulation is two-dimensional.…”

“…Previous single-crystal neutron diffraction studies [5] have revealed that the magnetic structure of phase I (zero-field high-temperature phase) is described by the magnetic propagation vector Q ¼ (4/17 0 0) with an arrangement of ferromagnetic and paramagnetic (2 0 0)/(1 0 0) planes in the one-dimensional sequence along the a-axis of 0444404444, where '0', '4' and '4' denotes a paramagnetic plane, and four consecutive ferromagnetic planes with the moment parallel and anti-parallel to the c-axis, respectively, in a magnetic unit cell of 17a  a  c, where a and c are lattice constants of the original chemical cell. On the other hand, the magnetic structure of phase II (zero-field low-temperature phase) becomes two-dimensional with the same Q (2 0 0)/(1 0 0) planes with the phase difference p, containing one frustrated paramagnetic Tb ion at the corner and body-centered positions, respectively [5]. These planes are a kind of discommensuration compared with normal ferromagnetic (2 0 0)/(1 0 0) planes, and should be called mixed planes after Garnier et al [6].…”