Tadashi Kawamata

Magnetic Properties of (Cr1-xFex)O2

The solubility limit of Fe-ion in CrO2 and the properties of (Cr1-xFex)O2 were examined. Added Fe-ions dissolve into CrO2 and form an oxide of (Cr1-2x4+Crx5+Fex3+)O2, up to the x-value of about 0.06. The Tc increases from 116°C for the pure CrO2 to about 155°C with an Fe-addition of x=0.06. The magnetic moments of Fe3+ and Cr5+ couple in anti-parallel way to that of Cr4+.

Sulfur Modified Chromium Dioxide

It was found that sulfur ions dissolved in chromium dioxide up to about 3 atomic percent lowering both the Curie temperature, Tc, and the saturation magnetization, σs. As the amount of sulfur increased, the lattice constant of the crystal, a0, increased from 4.423 A to about 4.435 A, while no change was observed for c0. The addition of sulfur did not change substantially the size of the powder. The coercive force, Hc, at room temperature was as much as 120 Oe. The combined addition of sulfur and tellurium, however, resulted in a fine acicular powder with a coercive force higher than 400 Oersted and a Curie temperature of about 100°C. This powder has potential use in thermal duplication of magnetic tape signals.