A Study of Structural and Physical Properties of Heavily Co-doped LaSr2Mn2O7 Bi-layered Manganite

In this paper, we report the influence of cobalt doping on the structure and magnetic properties of bilayered-perovskite LaSr₂Mn_2?x Co _x O₇ (x=0.25,0.3). Parent and doped samples were synthesized through the sol-gel method under optimized conditions. X-ray diffraction studies coupled with the Rietveld refinement of xrd data, show that both doped and parent samples crystallize in a Sr₃Ti₂O₇-type layered perovskite structure. Temperature dependent magnetic behavior of the parent sample exhibits an antiferromagnetic and a charge-ordering state around 220 K. Magnetic field dependence of magnetization M(H) for doped samples at 20 K show well-defined M–H loops confirming the formation of intrinsic ferromagnetic ordering due to the Co doping. Additionally, we studied the ac–magnetic susceptibility and magnetization relaxation process in our samples. Dynamic scaling analysis hints an existence of glassy magnetic states in doped samples. Electrical and magnetic properties of our samples further demonstrate that Co doping suppresses charge ordering in bilayered LaSr₂Mn₂O₇.