Magnetic Phase Separation in La_1-xSr_xCoO₃ by ⁵⁹Co Nuclear Magnetic Resonance

⁵⁹Co NMR measurements on La_1-xSr_xCoO₃ reported here establish unequivocally, for the first time, the coexistence of ferromagnetic regions, spin-glass regions, and hole-poor low spin regions at all x values from 0.1 to 0.5. A zero external field NMR spectrum, which is assigned to the ferromagnetic regions, has a spectral shape that is nearly x independent at 1.9 K, as are the relaxation times, T₁ and T₂. The integrated spectral area increases rapidly with x up to x=0.2 and then decreases slightly for larger x. In a field of 9.97 T, a narrow NMR line is observed at 102 MHz, identical to that found in x=0 samples in previous work. The integrated intensity of this spectrum decreases rapidly with increasing x, and is ascribed to hole-poor low spin regions. Beneath this spectrum, a third broad line, with a peak at 100 MHz, is assigned to a spin- or cluster-glass-like phase.