MAGNETIC-PROPERTIES OF RARE-EARTH-BASED MISFIT LAYERED MATERIALS OF FORMULA (LNS)NNBS2 (LN = LANTHANIDES, Y)

Crystallographic, transport and magnetic properties of several compounds of formula (LnS)nNbS2(Ln = Y, La, Ce, Nd, Sm, Gd) are presented. These compounds belong to the so-called misfit sandwiched layered phases where two-layered \LnS\ and \NbS2\ sublattices alternate along the c axis, the misfit between both sublattices occurring along the a axis. Single-crystal resistivities measured in the a-b plane present definite anomalies at T < 2.5 K for Ln = Y, La, Ce, Sm, which could be interpreted as superconducting transitions, similar to those found, for instance, in the lead- or tin-based compounds. Magnetic properties, essentially due to the \LnS\layers, show a wide variety of behaviours where the intrinsic anisotropy of the material is a determinant factor. The main features observed are as follows: 'local' moments due to either charge-transfer mechanisms or extrinsic effects, or both together, for Ln = La; crystal-field effects and magnetic order at 1.95 K for Ce; a trivalent H-6(5/2) magnetic configuration for Ln = Sm; antiferromagnetic order at T(N) = 4.6 K for Gd; important magnetic anisotropy and crystal-field effects for Nd. Spin-flop mechanisms are apparent for the cerium and gadolinium compounds. For all lanthanides presented in this work, a trivalent state is found, in agreement with the lattice constant parameters.