Development of thermoelectric Bi-based cobaltites with an easy axis of magnetization parallel to the c-axis for magnetic alignment

We report the conversion of the easy axis of magnetization from the c-axis to the c-axis in thermoelectric misfit-layered Bismuth-based cobaltites for a magnetic grain-alignment process. The conversion was accomplished by the substitution of Ca for Sr in the block layer of [(B_0.5Pb _0.5)₂Sr₂O₄]₂Sr ₂O₄]_0.55.CoO₂ Moreover, magnetic anisotropy along the c-axis was enhanced by partial substitution of Pr for Ca in [(Bi_0.5Pb_0.5)₂Ca₂O ₄]_zCoO₂. From the analysis of their crystal structures, we concluded that the doping of Pr and Ca played a role in distortion of the block layer, indirectly leading to changes in the local structure of the CoO₂ layers and magnetic anisotropy. The c-axis grain-aligned bulk has been successfully fabricated by a magnetic grain-alignment method in 10 T, and a drastic reduction in the resistivity perpendicular to the applied field and the grain-oriented microstructure were observed. magnetic alignment, easy axis of magnetization, thermoelectric materials, [Bi₂Sr₂O₄]_0.55CoO ₂, misfit crystal structure