Effect of Co doping on the magnetotransport properties of La0.45Sr0.55MnO3 perovskite

We investigated the magnetotransport properties of polycrystalline La0.45Sr0.55Mn1-xCoxO3 (0 <= x <= 0.15). Ferromagnetism is enhanced with the doping of Co ions in La0.45Sr0.55MnO3, but the antiferromagnetism is nearly destroyed in the low-temperature region. The Mn3+-Mn4+ double-exchange (DE) and Co2+-Mn4+ ferromagnetic (FM) superexchange interactions are mainly responsible for the magnetic properties of the doped system. With increased Co doping, the insulating properties and the magnetoresistance (MR) effect are simultaneously enhanced. This indicates that the Co doping strengthens both the Mn3+-Mn4+ DE and Co2+-Mn4+ FM superexchange interactions. The Co doping increases the disorder in the system, causing the MR effect to increase with decreasing temperature. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3117186]This work was supported by the Korea Science and Engineering Foundation grant funded by the Korea government (MEST) (Quantum Photonic Science Research Center, Korea)