Hidden magnetic transitions in the thermoelectric layered cobaltite<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>[</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ca</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">CoO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mo>]</mml:mo></mml:mrow><mml:mro

Sugiyama, Jun; Brewer, Jess H.; Ansaldo, Eduardo J.; Itahara, Hiroshi; Dohmae, Kazuhiko; Seno, Yoshiki; Xia, Changtai; Tani, Toshihiko

doi:10.1103/physrevb.68.134423

Cited by 119 publications

(95 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Seebeck coefficient reaches a large value of 130 µV/K at around 150 K, and becomes almost temperature independent up to 400 K, as described within the modified Heikes formula in which the spin and orbital degrees of freedom of correlated Co 3d electrons are involved [20,21]. On the other hand, the Seebeck coefficient again increases with increasing temperature above 400 K, suggested to be associated with a spin-state crossover [12], but the hightemperature spin-state nature of Ca 3 Co 4 O 9 remains puzzling [22,23]. Note that the similar issue regarding an excited spin state is greatly debated in the perovskite LaCoO 3 [24][25][26][27].…”

Section: Introductionmentioning

confidence: 86%

See 1 more Smart Citation

Thermoelectric transport in the layered Ca3Co4–xRhxO9 single crystals

Ikeda

Saito

Okazaki

2016

Journal of Applied Physics

View full text Add to dashboard Cite

We have examined an isovalent Rh substitution effect on the transport properties of the thermoelectric oxide Ca 3 Co 4 O 9 using single-crystalline form. With increasing Rh content x, both the electrical resistivity and the Seebeck coefficient change systematically up to x = 0.6 for Ca 3 Co 4−x Rh x O 9 samples. In the Fermi-liquid regime where the resistivity behaves as ρ = ρ 0 + AT 2 around 120 K, the A value decreases with increasing Rh content, indicating that the correlation effect is weakened by Rh 4d electrons with extended orbitals. We find that, in contrast to such a weak correlation effect observed in the resistivity of Rh-substituted samples, the low-temperature Seebeck coefficient is increased with increasing Rh content, which is explained with a possible enhancement of a pseudogap associated with the short-range order of spin density wave. In high-temperature range above room temperature, we show that the resistivity is largely suppressed by Rh substitution while the Seebeck coefficient becomes almost temperature-independent, leading to a significant improvement of the power factor in Rh-substituted samples. This result is also discussed in terms of the differences in the orbital size and the associated spin state between Co 3d and Rh 4d electrons.

show abstract

Section: Introductionmentioning

confidence: 86%

“…It is theoretically suggested that a mixture of low-spin and high-spin states may enhance the Seebeck coefficient [20]. Thus, a thermally-induced spinstate crossover from low-spin into higher-spin state is suggested for the enhancement of Seebeck coefficient [12], but the nature of spin states at high temperatures is still puzzling [22,23].…”

Section: Discussionmentioning

confidence: 99%

Thermoelectric transport in the layered Ca3Co4–xRhxO9 single crystals

Ikeda

Saito

Okazaki

2016

Journal of Applied Physics

View full text Add to dashboard Cite

show abstract

“…Ferrimagnetic or very weak ferromagnetic-like properties are also observed at low temperature [7]. In addition, µ + SR experiments have been interpreted with the presence of a spin density wave at low temperature [8], giving a clue for a gap opening near the Fermi level leading to the observed "Fermi liquid"-insulator transition. Nevertheless, the low temperature transport behavior is not really understood, specially because the ground state of the system is quite complex.…”

mentioning

confidence: 99%

Out-of-equilibrium electronic transport properties of a misfit cobaltite thin film

Pautrat¹,

Eng²,

Prellier³

2005

Phys. Rev. B

View full text Add to dashboard Cite

We report on transport measurements in a thin film of the 2D misfit Cobaltite Ca3Co4O9. Dc magnetoresistance measurements obey the modified variable range hopping law expected for a soft Coulomb gap. When the sample is cooled down, we observe large telegraphic-like fluctuations. At low temperature, these slow fluctuations have non Gaussian statistics, and are stable under a large magnetic field. These results suggest that the low temperature state is a glassy electronic state. Resistance relaxation and memory effects of pure magnetic origin are also observed, but without aging phenomena. This indicates that these magnetic effects are not glassy-like and are not directly coupled to the electronic part. [5]. Furthermore, there is a possibility of frustrated magnetic interactions in a kagome lattice in the CoO 2 layers [6]. Ferrimagnetic or very weak ferromagnetic-like properties are also observed at low temperature [7]. In addition, µ + SR experiments have been interpreted with the presence of a spin density wave at low temperature [8], giving a clue for a gap opening near the Fermi level leading to the observed "Fermi liquid"-insulator transition. Nevertheless, the low temperature transport behavior is not really understood, specially because the ground state of the system is quite complex. The eventual link between all these observations and the measured transport properties has to be clarified. The above mentioned results suggest that low dimensionality, frustration and disorder, together with strong electronic correlations, can be important features for the physical properties of the Ca 3 Co 4 O 9 system. Since they are known to reinforce fluctuations and metastability, one can expect a strong influence on the transport properties. To our knowledge, this has not been verified by the usual macroscopic transport measurements. Because of the statistical averaging, the discrete nature of the underlying "mesoscopic" processes can be masked in a bulk sample but revealed in a smallarea system. In this case, the transport measurements can be used as an efficient probe to bring some light on the ground states of the system [9].In this paper, we report a study of DC magnetotransport properties and of resistance fluctuations in a microbridge of a Ca 3 Co 4 O 9 thin film at low temperature. We particularly focus on the origin (magnetic or electronic) of these resistance fluctuations and relaxation.A 2000Å epitaxial thick film of Ca 3 Co 4 O 9 was used for the measurements. The film was deposited on (0001) Al 2 O 3 using the pulsed laser deposition technique. The details of the optimization, growth conditions and structural characterizations have been described previously [10]. Prior to the transport measurements, a silver layer was firstly deposited via thermal evaporation onto the film, and secondly a gold layer via RF sputtering. Microbridges (L = 200 µm × W = 50 µm) were then patterned with UV photolithography and argon ion etching. Thin aluminum contact wires were finally used to connect the areas to the electrodes w...

show abstract

“…[1,2,3,4,5] Several researchers reconfirmed later the existence of long-range magnetic order in the layered cobaltites by not only µ + SR [6] but also neutron diffraction experiments. [7] These cobaltites share a common structural component as a conduction path, i.e., the CoO 2 planes, in which a two-dimensional-triangular lattice of Co ions is formed by a network of edge-sharing CoO 6 octahedra.…”

Section: Introductionmentioning

confidence: 93%

“…On the contrary, it was found that not A TF but λ TF exhibit an anomaly at the spin state transition in the layered cobaltites. [3] Since each chain is considered to act as a single spin, we ignore the intra-chain 1D F interaction. Within the mean field theory, T N is expressed by; where z is the number of the nearest neighboring spins, J AF is the 2D AF coupling constant and k B is the Boltzmann constant.…”

Section: Figures 4(a) -4(d)mentioning

confidence: 99%

Two dimensionality in quasi-one-dimensional cobalt oxides

Sugiyama

Nozaki

Brewer

et al. 2006

Physica B: Condensed Matter

Self Cite

View full text Add to dashboard Cite

By means of muon spin rotation and relaxation (µ + SR) techniques, we have investigated the magnetism of quasi one-dimensional (1D) cobalt oxides AEn+2Con+1O3n+3 (AE=Ca, Sr and Ba, n=1, 2, 3, 5 and ∞), in which the 1D CoO3 chain is surrounded by six equally spaced chains forming a triangular lattice in the ab-plane, using polycrystalline samples, from room temperature down to 1.8 K. For the compounds with n=1 -5, transverse field µ + SR experiments showed the existence of a magnetic transition below ∼100 K. The onset temperature of the transition (T on c ) was found to decrease with n; from 100 K for n=1 to 60 K for n=5. A damped muon spin oscillation was observed only in the sample with n=1 (Ca3Co2O6), whereas only a fast relaxation obtained even at 1.8 K in the other three samples. In combination with the results of susceptibility measurements, this indicates that a two-dimensional short-range antiferromagnetic (AF) order appears below T on c for all compounds with n=1 -5; but quasi-static long-range AF order formed only in Ca3Co2O6 , below 25 K. For BaCoO3 (n=∞), as T decreased from 300 K, 1D ferromagnetic (F) order appeared below 53 K, and a sharp 2D AF transition occurred at 15 K.

show abstract

Hidden magnetic transitions in the thermoelectric layered cobaltite[Ca2CoO3]

Cited by 119 publications

References 35 publications

Thermoelectric transport in the layered Ca3Co4–xRhxO9 single crystals

Thermoelectric transport in the layered Ca3Co4–xRhxO9 single crystals

Out-of-equilibrium electronic transport properties of a misfit cobaltite thin film

Two dimensionality in quasi-one-dimensional cobalt oxides

Contact Info

Product

Resources

About