Exchange bias and magnetoresistance effects in La2-xSrxCoMnO6 (0.05 ≤ x ≤ 0.5)

Double perovskites with Sr2+-doping at the A-site in La2-xSrxCoMnO6 (0.05 ≤ x ≤ 0.5) are synthesized by the standard solid-state reaction method. X-ray diffraction indicates that the initial monoclinic crystal structure transforms to rhombohedra with the increasing Sr-doping from x = 0.05 to 0.5. The Sr-doped samples (0.1 ≤ x ≤ 0.3) possess mixed crystallographic phases with monoclinic and rhombohedra structure. The appropriate amount of Sr-doping (x = 0.3) can effectively increase exchange bias effect to reach a maximum value of 6.5 kOe (at 5 K) under the 10 kOe cooled magnetic field. The exchange coupling of uncompensated magnetic moment at the interface between ferromagnetic and antiferromagnetic phases is responsible for the variation trend of exchange bias effect. A large enhanced negative magnetoresistance effect (approximately 67.1%) of the x = 0.3 sample is observed at 85 K and 70 kOe. The reduction of the density of spin polarization states at Fermi level caused by disorder of Co/Mn ions is the reason for the decreasing magnetoresistance effect in the multiple Sr-doping (x > 0.3).