The oxidation and magnetic properties of MP recording media particles

MP recording media pigments have been subjected to elevated temperatures of 180/spl deg/C in air at various rates of heating from room temperature. It has been found that the rate of heating of these particles determines the final oxide which the particles form. Analysis of the switching field distribution (SFD) of such particles before and after oxidation shows a broadening of the SFD to lower switching fields. A comparative analysis with X-ray spectra performed on the oxidized particles indicates that particles with lower values of coercivity have been oxidized preferentially.