Unconventional Hall effect in orientedCa3Co4O9thin films

Thermoelectric transport in the layered Ca3Co4–xRhxO9 single crystals

“…Hsieh et al have shown that the decrease of T/S with lowering temperature originates from the decrease of the carrier concentration n according to Eq. (2) [18], which is also supported from the results of the Hall coefficient measurements [38], and proposed that this phenomenon is ascribed to an opening of the pseudogap caused by the short-range order of SDW below 100 K [19]. We also note that such a reduction of T/S below a pseudogap temperature is observed in other layered cobalt oxide [39] and the Kondo semiconductor CeNiSn [40].…”

Spin-entropy contribution to thermopower in the[Ca2CoO3–t]0.62Hejtmánek1, Jirák2, Šebek3 2015Phys. Rev. B170100View full textAdd to dashboardCite

“…The magnetization curves at 2 K ( namely the existence of resistivity minimum and the charge carrier localization at the lowest temperature, see also [6]. As shown in the inset of Fig.…”

“…As the crystal structure is concerned, these systems have in common hexagonal layers of edge shared CoO 6 octahedra, in which electrical transport is carried out. These CoO 2 layers alternate with planes of variable content of Na + ions or, in the "misfits", there are interpolating blocks of two-, three-, or four-plane oxide layers of rock-salt (RS) type.…”

“…(IS) or high-spin (HS) character [6,7,8]. In that case the hole concentration in conducting CoO 2 layers is nominally n=0.38, but it is decreased to about n=0.32 hole per CoO 2 due to some oxygen deficiency in RS blocks at standard sample preparation, typically t≈0.05.…”

Thermoelectric properties of the misfit cobaltate Ca3Co4O9

“…3 and 14, the rock-salt subsystem mainly shortens the phonon mean free path and thus lowers the thermal conductivity, while the hexagonal subsystem is responsible for the electrical conductivity. In addition, the magneto-transport properties are remarkable [2,10,17]; in particular, a high-temperature (above 600 K) spin state transition has been discovered very recently [36,37].…”