Hall resistivity of RBaCo2O5.5 (R=Y and rare earth elements)

Hall resistivity ρH of polycrystalline samples of TbBaCo2O5.53 has been studied in detail under various external magnetic fields H. At metal-insulator transition temperature TMI, ρH exhibits a significant increase with decreasing temperature T, indicating that the number of the conduction electrons in the eg-orbitals of Co3+ ions of the CoO6 octahedra decreases. We have also observed unusual behavior of the magnetic field dependence of ρH in the transition region where the antiferromagnetic phase changes to the ferromagnetic one. Based on the results of the previous magnetic structural analyses, we discuss the relationship between the non-collinear spin structure and the anomalous Hall resistivities