Structural-distortion modes and transport properties of La0.5Ca0.5MnO3 by co-doping Dy3+ and Sr2+ ions

La0.5-xDyxCa0.5-ySryMnO3 (X = 0, 0.05, 0.08, 0.1, 0.14, 0.16, 0.2) polycrystalline samples were prepared by hightemperature solid-state reaction. The A-site disordering is increased with the doping concentration x, and meanwhile the average ionic radius of A-site is kept constant. X-ray diffraction and Raman spectroscopy were combined to investigate the microstructural distortion of MnO6 octahedron. Results show that the rotational vibration (RV) is the dominant distortion mode. With the A-site disordering increasing, RV mode is obviously hardened, and the Jahn-Teller distortion is enhanced. Properties investigation shows that the insulation is strengthened because of FM double exchange effect suppressed with A-site disordering increasing, and the magnetoresistance effect is weakened. A relatively significant magnetoresistance effect was observed in the low temperature region for the high-doped concentration sample, which may be related to the strong magnetic moment of Dy3+.