Inhomogeneous Magnetic State above the Curie Temperature of the Doped Cobaltite La1-XSrxCoO3

Results of structural neutron diffraction study and data on the transport and magnetic properties (the linear and nonlinear (second and third order) susceptibilities) are reported for the La1-xSrxCoO3 (x = 0.18 and 0.2) polycrystals. The data on the linear and third-order susceptibilities show indications of a long - range ferromagnetic ordering with the Curie temperature (T-C) about 180 K. Measurements of the second harmonic of the magnetization in the parallel ac and steady (H) magnetic fields (M-2(H,T)) reveal the appearance of ferromagnetic clusters in a paramagnetic matrix below some temperature (T*) above T-C. The characteristics of this clustered state and the stages of its temperature evolution are reliably determined since the non-ferromagnetic matrix affects weakly this state. is found that a spontaneous nucleation of the ferromagnetic clusters occurs below P, and their concentration increases sharply on cooling. Upon further decreasing temperature, the isolated clusters coalesce, leading to a percolative - type origination of a ferromagnetism. The M-2(H,T) response of isolated clusters and its T-variation, including the onset of the coalescence, are very close to those found in the doped manganites, which supports an assumption on a common origin of the clustered state in these compounds.