On the microscopic origin of the magneto-electronic phase separation in Sr doped LaCoO3

The nanoscopic magneto-electronic phase separation in doped La1-xSrxCoO3 perovskites was studied with local probes. The phase separation is directly observed by M\"ossbauer spectroscopy in the studied doping range of 0.05 <= x <= 0.25 both at room-temperature as well as in the low temperature magnetic phase. Extended with current synchrotron based X-ray spectroscopies, these data help to characterize the volume as well as the local electric and magnetic properties of the distinct phases. A simple model based on a random distribution of the doping Sr ions describes well both the evolution of the separated phases as well as the variation of the Co spin state. The experiments suggest that Sr doping initiates small droplets and a high degree of doping driven cobalt spin-state transition, while the Sr-free second phase vanishes rapidly with increasing Sr content.