The dc magnetic field, frequency, and temperature dependence of electromagnetic absorption at rf frequencies of 335 kHz and 10 MHz are measured in the as sintered samples of colossal magneto resistive materialsLa0.7Sr0.3MnO3andLa0.7Ca0.3MnO3by measuring the penetration depth using the method of Schawlow and Devlin. Very large magneto-electromagnetic absorption effects, much larger than the magneto resistive effects, are observed. A dc magnetic field of 1000 G changes the penetration depth at 350 kHz by 53&percent; at room temperature inLa0.7Sr0.3MnO3,whereas the resistance of the sample only decreases by 0.75&percent; for the same field. The effects are primarily a result of the decrease of the permeability of the sample with dc magnetic field in the ferromagnetic state. A simple dc magnetometer employing the as sinteredLa0.7Sr0.3MnO3contained in the coil of anLCoscillator as the sensing element is described.