The present invention provides a ferromagnetic chromium oxide powder having an additive of sulfur incorporated therewith, which powder has a lower curie temperature than that of pure chromium dioxide powder and a high saturation magnetization. Said powder has a composition in weight percent, consisting essentially of 61.90 to 57.22 percent of chromium and 0.0038 to 15.10 percent of sulfur. Moreover, the ferromagnetic chromium oxide powder having a combination of sulfur and further additives selected from tellurium, tin and antimony has a lower Curie temperature than that of pure chromium dioxide together with a high intrinsic coercive force and a high saturation magnetization. The particles of these powders are in a uniform acicular shape and are useful in magnetic recording media, especially for slave tapes in thermo-magnetic duplication.