EFFECTS OF COMPOSITION AND PROCESSING ON PROPERTIES OF MODIFIED MAGHEMITE FOR HIGH-DENSITY RECORDING

The effects of composition and processing on the magnetic properties of Co, Mn and Zn modified maghemite particulates obtained by coprecipitation from aqueous solutions and heat treatment have been explored. It was found that the saturation (at 2 T) magnetization, of 63-75 emu/g and residual magnetization of 45-52 emu/g change little with the composition studied (6-14.4 wt% Mn and 8-15 wt% Co), while coercivity (1100-2200 Oe) does. The temperature coefficient of coercivity (TCC) was -0.24 to -0.39%/degrees-C, depending only on composition. The Co content was found to dominate coercivity, while Mn led to a better heat treatment response of the particulates. Low-level Zn doping enhanced magnetization and reduced the TCC.