Misfit layer compounds family (MS)nTS2(M = Sn, Pb, Bi, rare earth element;T= Nb, Ta;n= 1.08–1.19)

Publisher Website
Google Scholar
Abstract
Compounds (MS) n TS2, where M is a rare earth element, tin, lead or bismuth and T is a transition metal, constitute a new family of incommensurate materials. They are built up from a succession of |MS| and |TS2| slabs. Each |MS| slab is a distorted NaCl type double layer, where M surrounding is a distorted square pyramid of S atoms. T coordination is trigonal prismatic in |TS2| sandwich, which is very similar to those of 2H-TS2 structures. X-ray diffraction of each type of slab shows that one intralayer lattice parameter of |MS| slab is incommensurate with the corresponding one of a |TS2| slab. Both layers are then commensurate along the stacking axis and one perpendicular direction, and misfitted in any other direction. This misfit is directly responsible for the formulation, e.g. (LaS)1.14NbS2 or (SnS)1.18NbS2. As is shown for (LaS)1.14NbS2, three different approaches were used for the structural determination of these compounds by X-ray diffraction: The very anisotropic electrical transport and magnetic properties can be interpreted by considering that |MS| slabs are intercalated in a |TS2| structure with some charge transfer. These compounds are low-Tc (some K) superconductors. Nevertheless, these members of the very wide misfit layer compounds family are very interesting as a tool for investigations of interactions leading to incommensurability.