SPIN-GLASS-LIKE BEHAVIOR OF THE INCOMMENSURATE COMPOSITE PHASE LACRS3

(La0.95V0.05S)(1.19)CrS2 (V stands for vacancy, often abbreviated ''LaCrS3'') belongs to the family of composite misfit layer compounds with a structural formulation [MX](1+x)(TX(2))(m) [G. A. Wiegers and A. Meerschaut, in Incommensurate Sandwiched Layered Compounds, edited by A. Meerschaut (Trans. Tech. Pub., Zurich, 1992)]. Chromium is the only magnetic element and antiferromagnetic interactions (theta(p) = -390 K) between chromium atoms [d(Cr-Cr)(av) 3.435 Angstrom] are taking place. At low temperatures (T < 80 K), the susceptibility is largely dependent of the cooling mode: ZFC (zero field cooled) and FC (field cooled). A great number of measurements were performed: magnetization, thermo- and isothermal remanent magnetization, and ac susceptibility on powder and on a single crystal. They all show that LaCrS3 has complex magnetic properties which are reminiscent of spin-glass behavior. These experimental results are discussed in relation with the crystal structure which shows two peculiarities: the (1) chromium framework is a two-dimensional triangular lattice in which antiferromagnetic coupling leads to a topological frustration; and (2) the structural modulation resulting from the mutual interaction between both sublattices (\LaS\ and \CrS2\) leads to J/k coupling constant values ranging from -60 to -10 K, in relation to the d(Cr-Cr) distribution [3.37 Angstrom < d(Cr-Cr) < 3.48 Angstrom]. These two structural characteristics (frustration and modulation) can explain the formation of magnetic domains in which magnetic moments are not exactly compensated. The resulting moments of these domains are in interaction and can be frozen in the easy magnetization direction giving this compound a spin-glass-like behavior.