Independent magnetic switching units in cobalt-doped iron oxide particles

The dependence of measured coercivity upon the time-scale of the experimental method can be used to estimate the volume of the magnetic switching unit; this approach has generally given values in good agreement with the particle volumes estimated from transmission electron microscopy (TEM) for iron oxide magnetic recording materials. This paper presents data relating to novel cobalt-doped iron oxide particulate materials, of potential use in magnetic recording, in which the coercivity time-scale dependence implies a volume substantially smaller than the total particle volume. Some possible explanations for this behavior are discussed.