Sulfur modified chromium dioxide

Chromium dioxide modified with sulfur has been studied with the intention of obtaining a magnetic powder which is suitable for the tape of thermomagnetic duplication. Sulfur ions dissolve into CrO2up to about 0.17 wt.% and decrease the Curie temperature and saturation magnetization. With added sulfur of about 1 wt.%, the Tc of chromium dioxide is lowered by 20°C and the σsbecomes about 70 EMU/g. The lattice parameter a0increases with increasing sulfur, while c0shows no change. The CrO2with only a sulfur modifier does not have fine acicular shape. Therefore, the combined addition of S and Te was tried. The S-Te-modified CrO2has Tcof 100°C, Hcof 400 Oe and σsof 81 EMU/g. The particle shape of this oxide is about 0.5 μm in average length and 10/1 in length to width ratio. This powder has high potential for use in the magnetic tape of thermal duplication.