FMR OF POWDER LA0.7CA0.3MNO3

We report the observation of ferromagnetic antiresonance and resonance in powder La0.7Ca0.3MnO3 at microwave frequencies of 22 GHz, 32 GHz a nd 36 GHz in the temperature range 77K - 350 K. Using different grain sizes we are able to place an upper limit on the resistivity of the gr ain and estimate the grain resistivity rho(grain) less than or equal t o Im Omega cm in the neighbourhood of the peak resistivity where the r eported bulk resistivity values are rho(bulk) approximate to 20 m Omeg a cm - 50 m Omega cm. This indicates that the grains appear to be at l east an order of magnitude more conducting than the bulk.