Transport and magnetic properties in YBaCo2O5.45:: Focus on the high-temperature transition

The electronic transport properties and the magnetic susceptibility were measured in detail in YBaCo(2)O(5.45). Close to the so-called metal-insulator transition, strong effects of resistance relaxation, a clear thermal hysteresis, and a sudden increase of the resistance noise are observed. This is likely due to the first order character of the transition and to the underlying phases coexistence. A positive and linear magnetoresistance is also observed, which can be linked to this heterogeneity. From a magnetic point of view, the paramagnetic to ordered magnetic state transition is observed using nonlinear susceptibility. This transition shows the characteristics of a continuous transition, and time dependent effects can be linked with the dynamics of magnetic domains in the presence of disorder. Thus, when focusing on the order of the transitions, the electronic one and the magnetic one cannot be directly associated.