ALTERNATING-CURRENT MAGNETIC-SUSCEPTIBILITY MEASUREMENTS IN LA1-XSRXCOO3 (X-LESS-THAN-OR-EQUAL-TO-0.30) BELOW 300-K

A dynamical magnetic susceptibility study on La1-xSrxCoO3 samples obta ined by a coprecipitation method is reported for x less than or equal to 0.30. For x < 0.20 differences between zero field cooled and field cooled de magnetic susceptibility appear at a temperature T-a below th e Curie point, T-C approximate to 240 K, as well as a magnetic freezin g point at a temperature T-b < T-a. Alternating current magnetic susce ptibility shows two maxima at these temperatures, which is interpreted as the evidence of different interaction processes between ferromagne tic clusters mediated by a matrix of changing spin-state Co3+ ions. Fo r x greater than or equal to 0.20 an unique blocking process seems to take place due to the percolation of the ferromagnetic clusters, makin g unimportant the contribution of the matrix. (C) 1997 American Instit ute of Physics.