The powder FMR of six ferrites at 9.1 GHz in the temperature range 25 to 290° C is reported in this paper. The effect of the internal fields on the linewidths and the resonance fields are studied. Curie temperatures obtained for some of the ferrites from FMR are compared with the values obtained from an oscillator technique. The line shapes are found to be of Lorenzian shape. Effective g values were calculated and a brief discussion is made about the various contributions to the total field. © 1985 Chapman and Hall Ltd.