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-Cr 2 Se 3 and trigonal-Cr 2 Te 3 have been measured in the temperature range between 15 K and 300 K. As T increases, a ( T ) for Cr 2 Se 3 increases up to a magnetic order-order transition temperature T t above which it suddenly shrinks with the change Δ a / a =-1.1×10 -3 , while c ( T ) smoothly increases through T t . In Cr 2 Te 3 , a ( T ) decreases up to about 250 K 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.