abstract |
Magnetic particles are cobalt surface treated gamma iron oxide (Fe 2 O 3 ) having a specific area of at least 30 m 2 /g and a powder coercivity greater than about 450 Oe, the particles being coated with from about 10 to about 50% by weight of a material having a refractive index less than about the refractive index of a binder for the particles. |