Indications of phase separation in polycrystalline La_1-xSr_xMnO₃ for x≈0.5

We present systematic studies of polycrystalline La_1-xSr_xMnO₃ where x is varied from 0.46 to 0.53 at 0.01 intervals. We have measured the magnetic resonance, ac susceptibility, dc magnetization, x-ray diffraction, four-probe resistivity, and optical reflectivity. The data seem to indicate that, at low T, the materials are intimate mixtures of ferromagnetic and antiferromagnetic microregions. For x>0.48 we observe anomalies pointing toward charge ordering on lowering T. An effective-medium theory is presented, and an appropriate phase diagram is proposed.