A One-Dimensional Magnetic System; Terbium Borosilicide

Boron-rich compounds such as REB$_{66}$ are well known, but the main interest has tended to be of structural or mechanical nature. However, recently interesting magnetic behavior has been discovered in B$_{12}$ icosahedra-containing dilute semiconducting f-electron compounds [1]. For example, the 3D long range order of GdB$_{18}$Si$_{5}$ and 2D spin glass behavior of a homologous series of higher borides like REB$_{17}$CN. An interesting aspect of these transitions is the indication that B$_{12}$ icosahedral clusters mediate the magnetic interaction, possibly through a superexchange mechanism. Results obtained for neutron diffraction and doping effects on a TbB$_{50}$-type compound TbB$_{44}$Si$_{2}$ are presented. It is indicated that this is a 1D system with extremely short range interaction. [1] e.g. T. Mori and H. Mamiya, Phys. Rev. B, {\bf 68}, 214422 (2003), T. Mori, J. Appl. Phys., {\bf 95}, 7204 (2004).