Nano-block integration in the misfit layered Co oxides

摘要

The layered cobalt oxides having the CdI{sub}2-type hexagonal CoO{sub}2 layer exhibit good thermoelectric properties especially at high temperatures. Above all, the misfit layered Co oxides [A{sub}2M{sub}nO{sub}(2+n-d)]{sub}yCoO{sub}2 are of particular interest, in which the CoO{sub}2 layer and the NaCl-type tetragonal block-layer stack alternately along the crystallographic c axis. We prepared single crystals for various kinds of misfit layered Co oxide, and measured the thermoelectric properties to investigate how the block layer affects the electronic states of the CoO{sub}2 layer. We found that the room-temperature thermopower monotonically increases with the misfit ratio y, which we associated with short-ranged spin-density-wave modulated by the interfacial stress between the layers.