Magnetic phase separation in La1-xSrxCoO3 by 59Co NMR

Abstract

59Co NMR measurements on La1-xSrxCoO3 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 which 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 becomes almost constant 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, centered at 100 MHz, with shorter T1 and T2,. is assigned to a spin glass, intermediate spin phase.