Abstract
Giant diamagnetism, with values to − 1.4·10−2 emu/g, was observed from 4.2 K to 310 K in selenides of monoclinic NiAs structure prepared with stoichiometries FeSe·uCr2Se3, u = 0.1 to 1.0. A positive component due to magnetic order of the spins was present from 4.2 K to about 65 K-150 K, depending on the sample. The magnetic order was minimized by doping with As0.3Ge0.3. Another sample doped with Ga and Ge gave a decrease in the slope of negative susceptibility vs T(K) starting at 220 K and thus an increase in the range of diamagnetism to well over ambient temperature.