Impact of Co doping on magnetic and electrical properties of La0.5Ca0.5Mn1−xCoxO3 (0≤x≤0.05) manganites

• Results shows that the magnetization increases initially by Co doping and then decreases.
• Results shows that 0.5% Co doping induces insulator–metal transition in the undoped sample.
• We report a feature of inverted thermal hysteresis loop for 0.0075≤x≤0.05 samples.
• A magnetic instability is reported for x=0 and 0.005 samples.

In this study, structural, magnetic and electrical properties of polycrystalline La0.5Ca0.5Mn1−xCoxO3 (x=0, 0.005, 0.0075, 0.01, 0.025 and 0.05) samples have been investigated using ac susceptibility, magnetization and resistivity measurements. Rietveld refinement of X-ray diffraction patterns indicates an orthorhombic structure with Pnma   space group for all samples. No structural transition is observed due to Co doping. Magnetic studies show that the magnetization and real parts of ac susceptibility (χ′(T))χ′(T)) increase initially by increasing x up to x=0.025 and decrease by further increase in x, up to x=0.05. The notable point of this study is the ability of a 0.5% of Co doping to induce insulator–metal transition in the insulating undoped sample at low temperatures. Also, we report a feature of thermal hysteresis behavior in La0.5Ca0.5Mn1−xCoxO3 series, which is the inverted thermal hysteresis loop for 0.0075≤x≤0.05 samples. In the Co doping level range of 0≤x  <0.0075, χ′(T)χ′(T) and resistivity (ρ(T)) curves show counterclockwise (CCW) and clockwise (CW) thermal hysteresis, respectively. On the other hand samples with 0.0075≤x  <0.05 Co doping level exhibit CW thermal hysteresis in χ′(T)χ′(T) and CCW one in ρ(T) curves. The thermal hysteresis behavior is attributed to the interfacial elastic energy in the boundary among the phases with different magnetic states. Magnetic instability is reported for x=0 and 0.005 samples and possible reasons for these behaviors are discussed.