Magnetic properties and charge ordering phase of La0.4Ca0.6Mn1-xCoxO3 system by Co substitution for Mn

A series of La0.4Ca0.6Mn1-xCoxO3(x=0.02, 0.04, 0.06, 0.08, 0.10, 0.12) samples were prepared using solid-state reaction method. The structure of the samples was analyzed by X ray diffraction (XRD), and the effects of Co substitution for Mn on the magnetic properties and charge ordering of La0.4Ca0.6MnO3 were studied by the measurements of magnetization-temperature (M-T) curves, resistivity-temperature (ρ-T) curve, electron spin-resonance (ESR) spectroscopy. The XRD patterns showed that all the samples were good single-phase, which indicated that Co entered into the site of Mn and formed good crystals. With the increase of doping Co, the resistivity and antiferromagnetism decreased, and the ferromagnetism increased. When x was 0.02, the charge ordering phase was almost melted. However, the charge ordering phase was melted completely with x=0.06. The electronic structure of Co3+ was 3d6 and Oh symmetrical, reducing the distortion of Jahn-Teller (JT). The decreased distortion of JT produced two influences: (1) the bond length of Mn3+-O2--Mn4+ shortened, and the bond angle increased, which favored a double exchange; (2) a band gap was formed between two eg orbits of Mn3+. However, the gap decreased with the Co3+ substitution for Mn3+, which could improve the conductivity and increased the ferromagnetism, leading to a destruction of charge ordered phase. ©, 2015, Editorial Office of Chinese Journal of Rare Metals. All right reserved.