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