摘要
Layered perovskite manganite ceramics with a nominal chemistry La1.5Ca1.5Mn2-xFexO7(x = 0.0, 0.05, 0.1, 0.3, 0.5) were prepared using sol-gel method. The manganese ions are highly mixed states of Mn3+ and Mn4+. It is found that the Mn3+/Mn4+ ratio decreases with the Fe doping content increasing. The conductivity and magnetoresistance (MR) were studied. The sample of x = 0.05 shows metal insulator transition (MIT) at 135 K. The MIT peak temperature (Tp) shifts towards higher temperature with increasing applied magnetic field. All the samples can be well fitted to the variable-range hopping (VRH) model. The maximum value of MR (%) [ρ(0) - ρ(H)]/ρ(0) × 100 for x = 0.05 is 34% (105 K, 7 kOe).
Layered perovskite manganite ceramics with a nominal chemistry La1.5Ca1.5Mn2-xFexO7(x = 0.0, 0.05, 0.1, 0.3, 0.5) were prepared using sol-gel method. The manganese ions are highly mixed states of Mn3+ and Mn4+. It is found that the Mn3+/Mn4+ ratio decreases with the Fe doping content increasing. The conductivity and magnetoresistance (MR) were studied. The sample of x = 0.05 shows metal insulator transition (MIT) at 135 K. The MIT peak temperature (Tp) shifts towards higher temperature with increasing applied magnetic field. All the samples can be well fitted to the variable-range hopping (VRH) model. The maximum value of MR (%) [ρ(0) - ρ(H)]/ρ(0) × 100 for x = 0.05 is 34% (105 K, 7 kOe).
