Spin line groups.

Spin line groups describe the symmetries of spin arrangements in quasi-one-dimensional systems. These groups are derived for the first family of line groups. Among them, magnetic groups are singled out as a special case. Spin arrangements generated by the derived groups are first discussed for single-orbit systems and then the conclusions are extended to multi-orbit cases. The results are illustrated by the examples of a CuO2 zigzag chain, a (13)C nanotube and the hexaferrite Ba2Mg2Fe12O22. Applications to neutron diffraction and classical ground-state determination are indicated.