Short-range charge order correlations in Sm1−xSrxMnO3 near a half-doped composition revealed by EPR

EPR study of polycrystalline Sm1−xSrxMnO3 samples (x=0.40, 0.45, 0.50) within the temperature range 100–500 K has revealed some details of its phase diagram. A change of the first-order ferromagnetic transition at TC≈130 K (for x=0.40, 0.45) into the second-order one (for x=0.50) was clearly demonstrated. Analysis of the EPR line intensities reveal a charge ordering above 250 K for all the compositions in spite of its short-range nature. For x=0.50 composition, a short-range antiferromagnetic ordering was also found below 170 K. The latter might be responsible for suppression of the first-order type of the ferromagnetic transition.