Giant 1/f Noise in Perovskite Manganites: Evidence of the Percolation Threshold

We discovered an unprecedented magnitude of the 1/f noise near the Curie temperature (T sub c) in low T sub c manganites. The scaling behavior of the 1/f noise and resistance provides strong evidence of the percolation nature of the ferromagnetic transition in the polycrystalline samples. The step-like changes of the resistance with temperature, observed for single crystals, suggest that the size of the ferromagnetic domains depends on the size of crystallites.