Nucleation and Development of Clustered State in La1-xSrxCoO3 and La1-xCaxCoO3 Single Crystals at x=0.15
Results of structural neutron diffraction study and data on the transport and magnetic properties (the linear and nonlinear (second and third order) susceptibilities) are presented for the La1-xSrxCoO3 and La1-xCaxCoO3 at x = 0.15 single crystals. It is founf that these compounds are insulators and exhibit the rhombohedral R3-c space group. According to the magnetic measurements, the development of the ferromagnetic (F) clustered state proceeds into three stages. On cooling, during the first stage, the F clusters nucleate at the preferential sites that are likely produced by variation in oxygen and doping stoichiometry. The second stage is characterized by sharp increasing the concetraion of the isolated F clusters on cooling. This is the process of the homogeneous nucleation. A coalescence of the isolated F clusters into some large-scale complexes containig some ammount of the domains is associated with the third stage. Note that it is the typical behavior observed at a first order phase transition. The data allow one to determined reliably the temperature boundaries of the stages.