Evidence of Variable Range Hopping (VRH) and Exchange Interaction in Co-Doped Multiferroic BiMnO3 Nanoparticles

Among ABO3-type oxides, centrosymmetric (C2/c) BiMnO3 is one of the few single-phase multiferroics, with a highly distorted perovskite structure that has been extensively studied. In this work, to stabilize the crystal structure, to control temperature dependence of electrical properties and to induce low coercivity at low temperature, strategy of doping transition metal has been adopted for useful applications. Well-crystallized single-phase cobalt-doped bismuth manganite nanoparticles having general formula BiCoxMn1−xO3 (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were synthesized by co-precipitation method. All compositions show that substituting Mn with Co, in BiMnO3-based compounds enhances better and more stable structural properties, like lattice parameters and crystallite size, phase transition temperatures, temperature-dependent DC electrical properties and magnetic properties. The extrinsic contribution to the temperature-dependent electrical properties is an increased resistivity due to charge localization. The magnetic properties due to transition metal doping are strongly affected by the super-exchange interaction phenomenon between Co3+ and Mn4+ cations.