THERMAL-EXPANSION IN CHROMIUM CHALCOGENIDES CR2X3 (X=SE, TE)

The lattice parameters a(T) and c(T) as a function of temperature (T) for rhombohedral-Cr2Se3 and trigonal-Cr2Te3 have been measured in the temperature range between 15 K and 300 K. As T increases, a(T) for Cr2Se3 increases up to a magnetic order-order transition temperature T, above which it suddenly shrinks with the change DELTAa/a=-1.1 x 10(-3), while c(T) smoothly increases through T(t). In Cr2Te3, a(T) decreases up to about 250K and then increases while c(T) increases in the temperature range measured. The obtained results are qualitatively discussed on the relation beteen the moment stability and volumetric expansion.