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A Maignan - One of the best experts on this subject based on the ideXlab platform.
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magnetodielectric coupling and magnetization plateaus in α cov2o6 crystals
Journal of Materials Chemistry, 2012Co-Authors: Kiran Singh, Olivier Perez, D Pelloquin, A Maignan, Ch SimonAbstract:Large crystals of the monoclinic α-CoV2O6 Cobaltite have been grown. A clear dielectric anomaly is found at 15 K which coincides with the magnetic ordering temperature. For large enough magnetic field values, this upturn in the e′(T) curve is suppressed. This is related to the different magnetic states (antiferro (AF), ferri (FI) and ferromagnetic (FO)) revealed by the isothermal magnetization curves. At 5 K, the magnetodielectric curves are found to mimic the M(H)T = 5 K curves: two abrupt changes are observed at HC1 = 1.65 T and HC2 = 3.3 T which correspond to the AF to FI and FI to FO transitions, respectively, and also hysteretic behavior for T < 5 K. These features demonstrate the strong coupling between magnetic and dielectric order parameters.
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orthorhombic kagome Cobaltite cabaco4o7 a new ferrimagnet with a tc of 70 k
Solid State Communications, 2009Co-Authors: V Caignaert, A Maignan, V Pralong, Bernard RaveauAbstract:Abstract A novel mixed valent Cobaltite CaBaCo 4 O 7 has been synthesized. Its structure, closely related to the LnBaCo 4 O 7 oxides of the “114” series, differs from the latter by a large orthorhombic distortion, involving a buckling of the CoO 4 tetrahedra of the kagome layers. Importantly, this new phase is ferrimagnetic with a T C =70 K and a very large coercive field of 2 T at 5 K, in contrast to LnBaCo 4 O 7 oxides, which exhibit magnetic frustration.
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dome shaped magnetic phase diagram of thermoelectric layered Cobaltites
APS, 2004Co-Authors: Jun Sugiyama, S Hebert, Jess H Brewer, E J Ansaldo, Hiroshi Itahara, Takao Tani, Masashi Mikami, Yusuke Mori, Takatomo Sasaki, A MaignanAbstract:Using muon spin spectroscopy we have found that, for both NaxCoO2 (0.6 ≤ x ≤ 0.9) and 3- and 4-layer Cobaltites, a common low temperature magnetic state (which in some cases is manifest as an incommensurate spin density wave) forms in the CoO2 planes. Here we summarize those results and report a dome-shaped relation between the transition temperature into the low-T magnetic state and the composition x for NaxCoO2 and/or the high-temperature asymptotic limit of thermopower in the more complex 3- and 4-layer Cobaltites. This behavior is explained using the Hubbard model on two-dimensional triangular lattice in the CoO2 plane.
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a new thermoelectric misfit Cobaltite sr2coo3 coo2 1 8
Solid State Sciences, 2004Co-Authors: D Pelloquin, S Hebert, A Maignan, Bernard RaveauAbstract:Abstract The study of the SrCoO system has allowed to isolate a new layered Cobaltite [Sr2CoO3][CoO2]1.8. The structural analysis by transmission electron microscopy shows a composite structure consisting in two substructures related to triple rock–salt-type layers and single CdI2-type layer, respectively. The structure of this compound is similar to that of the well-known misfit Cobaltite [Ca2CoO3][CoO2]1.62, also called “Ca3Co4O9”. The latter is intensively studied for thermoelectric power application to convert waste heat energy into electricity at temperature well above 300 K. A large thermoelectric power is also found for this new Cobaltite [Sr2CoO3][CoO2]1.8, which exhibits a Seebeck coefficient such as S 300 K ≈110 μV K−1. This value, lower than that of [Ca2CoO3][CoO2]1.62 ( S 300 K ≈125 μV K−1), shows that the misfit character, quantified by the ratio b1/b2=1.8 and 1.62 for the “Sr” and “Ca” based misfit Cobaltites, respectively, is directly connected to the thermoelectric properties in these materials.
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dome shaped magnetic phase diagram of thermoelectric layered Cobaltites
Physical Review Letters, 2004Co-Authors: Jun Sugiyama, S Hebert, Jess H Brewer, E J Ansaldo, Hiroshi Itahara, Takao Tani, Masashi Mikami, Yusuke Mori, Takatomo Sasaki, A MaignanAbstract:Using muon spin spectroscopy we have found that, for both Na x CoO 2 (0.6 ≤ x ≤ 0.9) and three- and four-layer Cobaltites, a common low temperature magnetic state (which in some cases is manifest as an incommensurate spin density wave) forms in the CoO 2 planes. Here we summarize those results and report an almost dome-shaped relation between the transition temperature into the low-T magnetic state and the composition x for Na x CoO 2 and/or the high-temperature asymptotic limit of thermopower in the more complex three- and four-layer Cobaltites. This behavior is explained using the Hubbard model on a two-dimensional triangular lattice in the CoO 2 plane.
Noemi Walsoe E De Reca - One of the best experts on this subject based on the ideXlab platform.
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high performance solid oxide fuel cell cathodes based on Cobaltite nanotubes
Journal of the American Chemical Society, 2007Co-Authors: Martin G Bellino, Joaquin Sacanell, D G Lamas, And Ana G Leyva, Noemi Walsoe E De RecaAbstract:A new generation of nanostructured cathodes for intermediate temperature solid-oxide fuel cells, with very low polarization resistance, is presented. They were prepared from Cobaltite nanotubes using a fast and simple method that allows the retention of the original nanostructure.
J A Kilner - One of the best experts on this subject based on the ideXlab platform.
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experimental visualization of the diffusional pathway of oxide ions in a layered perovskite type Cobaltite prbaco2o5 δ
Chemistry of Materials, 2013Co-Authors: Yi-ching Chen, Masatomo Yashima, J A Kilner, J PenamartinezAbstract:Layered perovskite-type Cobaltite PrBaCo2O5+δ is an oxide-ion and electronic mixed conductor with high oxide-ion conductivity and is promising for potential use in SOFC (solid oxide fuel cell) cathodes and oxygen membranes. The crystal structure and oxide-ion diffusional pathway of PrBaCo2O5+δ at 596 and 1000 °C have been investigated by in situ high-temperature neutron powder diffraction and a maximum-entropy method (MEM)-based nuclear-density analysis. The oxide ions of PrBaCo2O5+δ two-dimensionally and anisotropically diffuse through equatorial and deficient apical oxygen sites along the ⟨101⟩ directions in the Pr–Co–O ion-conducting slab.
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oxygen transport in selected nonstoichiometric perovskite structure oxides
Solid State Ionics, 1992Co-Authors: S Carter, A Selcuk, R J Chater, J Kajda, J A Kilner, B C H SteeleAbstract:New results on oxygen self-diffusion (D∗), surface exchange coefficient (k) and activation energy (Ea) of oxygen self-diffusion for chosen compositions of manganite and Cobaltite perovskites illustrate the effect of doping in the A and B sites of the ABO3 structure. The electrical conductivity (σT) was measured for the manganite group and permeability (J) was determined for the Cobaltite perovskites. D∗ increases with increasing x in La1−x(Sr,Ca)x(Mn,Co)O3−δ due to formation of new oxyge vacancies by introducing metals of lower valency (M2+) into the A3+ sites. A substitution of M2+ for B3+ or a reduction of the metal in the B3+ site to a lower positive valency also increases D∗ . D∗ Cobaltites is significantly higher than that of the manganites (by 4–6 orders of magnitude), however, the potentially high oxygen fluxes that would be allowed through the materials by the high D∗ values seem to be limited by the surface exchange kinetics. Ea-values of the manganites are considerably higher than those the Cobaltites. In general, the electrical conductivity, σT, decreased on doping the B site of the manganites with Co and Ni. However, whilst the pure manganite material exhibits a metallic type of conduction (i.e. σT decreased with increasing T), the conduction mechanism in the Co-doped and Ni-doped manganites changed to a localized hopping of charge carriers between the Mn3+ and Mn4+ sites (σT increases with increasing T).
Bernard Raveau - One of the best experts on this subject based on the ideXlab platform.
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cobalt oxides from crystal chemistry to physics
2012Co-Authors: Bernard Raveau, Md Motin SeikhAbstract:PREFACE CRYSTAL CHEMISTRY OF COBALT OXIDES Introduction Stoichiometric Perovskites LnCoO3 Stoichiometric Ln1-x AxCoO3 Perovskites (A Ca, Sr,Ba) Oxygen-Deficient Perovskites: Order-Disorder Phenomena in the Distribution of Anionic Vacancies The Ordered Double Stoichiometric Perovskite LaBaCo2O6 Hexagonal Perovskite and Derivatives The RP-Type Cobaltites: Intergrowths of Perovskite and Rock Salt Layers and Derivatives Cobaltites with a Triangular Lattice Some Other Original Cobaltites ELECTRONIC AND MAGNETIC PROPERTIES OF STOICHIOMETRIC PEROVSKITE CobaltiteS Stoichiometric LnCoO3 Perovskites Stoichiometric SrCoO3: Ferromagnetism and Metallic Conductivity Stoichiometric Ln1-xAxCoO3 Perovskites (A Ca, Sr, and Ba) The " Ordered " Double Stoichiometric Perovskite LaBaCo2O6 ELECTRONIC AND MAGNETIC PROPERTIES OF OXYGEN-DEFICIENT PEROVSKITE CobaltiteS SR1-XLNXCOO3-D AND SRCO1-XMXO3-D Disordered Perovskites Ordered 112 LnBaCo2O5+d Perovskites ELECTRONIC AND MAGNETIC PROPERTIES OF RUDDLESDEN-POEPPER-TYPE CobaltiteS Cobalt Valence and Spin State Transitions Magnetic Properties of RP Phases Electrical Properties of RP Phases Phase Separation in RP Phases Magnetoresistance of RP Phases Thermoelectric Properties of RP Phases ELECTRONIC AND MAGNETIC PROPERTIES OF CobaltiteS WITH A 3D "TRIANGULAR LATTICE" The Co3O4 Spinel and Derivatives The "114" LnBaCo4O7 and CaBaCo4O7 Cobaltites ELECTRONIC AND MAGNETIC PROPERTIES OF "TRIANGULAR" LAYERED CobaltiteS The Layer Sodium Cobaltites NaxCoO2 Misfit Cobaltites ELECTRONIC AND MAGNETIC PROPERTIES OF THE "UNIDIMENSIONAL" Cobaltite CA3CO2O6 Valence and Spin State of Cobalt Magnetic Properties of 1D-Ca3Co2O6 and Related Derivatives Electrical Resistivity of Ca3Co2O6 and Derivatives Magnetoresistance of Ca3Co2O6 Thermoelectric Power of Ca3Co2O6 and Derivatives
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oxygen excess in the 114 Cobaltite hexagonal structure the ferrimagnet cabaco4o7 50
Journal of Solid State Chemistry, 2011Co-Authors: Valerie Pralong, V Caignaert, Tapati Sarkar, O I Lebedev, Victor Duffort, Bernard RaveauAbstract:Abstract The study of the oxidation of the “114” orthorhombic Cobaltite CaBaCo4O7, using first electrochemistry and then soft chemistry based on oxidation by NaClO, has allowed a new phase, CaBaCo4O7.50, to be prepared topotactically. The structural study of this phase shows that its hexagonal structure, closely related to that of orthorhombic CaBaCo4O7, is curiously similar to that of the members of the LnBaCo4O7 series, in spite of its excess oxygen. Its magnetic study shows that this phase, like CaBaCo4O7, is ferrimagnetic with the same TC (60 K), but differently exhibits an unusual magnetic hysteresis. This exceptional behavior of CaBaCo4O7 with respect to oxidation as well as the magnetic properties of CaBaCo4O7.50 is interpreted in terms of the presence of defects due to oxidation.
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orthorhombic kagome Cobaltite cabaco4o7 a new ferrimagnet with a tc of 70 k
Solid State Communications, 2009Co-Authors: V Caignaert, A Maignan, V Pralong, Bernard RaveauAbstract:Abstract A novel mixed valent Cobaltite CaBaCo 4 O 7 has been synthesized. Its structure, closely related to the LnBaCo 4 O 7 oxides of the “114” series, differs from the latter by a large orthorhombic distortion, involving a buckling of the CoO 4 tetrahedra of the kagome layers. Importantly, this new phase is ferrimagnetic with a T C =70 K and a very large coercive field of 2 T at 5 K, in contrast to LnBaCo 4 O 7 oxides, which exhibit magnetic frustration.
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a new thermoelectric misfit Cobaltite sr2coo3 coo2 1 8
Solid State Sciences, 2004Co-Authors: D Pelloquin, S Hebert, A Maignan, Bernard RaveauAbstract:Abstract The study of the SrCoO system has allowed to isolate a new layered Cobaltite [Sr2CoO3][CoO2]1.8. The structural analysis by transmission electron microscopy shows a composite structure consisting in two substructures related to triple rock–salt-type layers and single CdI2-type layer, respectively. The structure of this compound is similar to that of the well-known misfit Cobaltite [Ca2CoO3][CoO2]1.62, also called “Ca3Co4O9”. The latter is intensively studied for thermoelectric power application to convert waste heat energy into electricity at temperature well above 300 K. A large thermoelectric power is also found for this new Cobaltite [Sr2CoO3][CoO2]1.8, which exhibits a Seebeck coefficient such as S 300 K ≈110 μV K−1. This value, lower than that of [Ca2CoO3][CoO2]1.62 ( S 300 K ≈125 μV K−1), shows that the misfit character, quantified by the ratio b1/b2=1.8 and 1.62 for the “Sr” and “Ca” based misfit Cobaltites, respectively, is directly connected to the thermoelectric properties in these materials.
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metallicity and thermopower of the misfit Cobaltite bi2ba1 8co0 2o4 rs coo2 2
Physical Review B, 2003Co-Authors: M Hervieu, A Maignan, C Michel, V Hardy, N Creon, Bernard RaveauAbstract:The misfit Cobaltite, [Bi 2 Ba 1 . 8 Co 0 . 2 O 4 ] R S [CoO 2 ] 2 , built up from the stacking of rocksalt-type layers (RS) and single hexagonal [CoO 2 ] layers (H), has been synthesized. This complex structure, described in a commensurate monoclinic supercell, exhibits a double commensurate modulation: a misfit modulation with b R S /b H =2 and an intrinsic modulation of the RS layers [q i =0.2(a R S +b R S )]. This oxide is characterized by an enhanced metallic behavior with respect to the misfit Bi(Pb)/Sr/Co/O Cobaltites and in contrast to these compounds by a positive magnetoresistance and significantly smaller values of the thermoelectric power (<100 μV K - 1 ). A comparison of its behavior with those of Sr 2 RuO 4 and of the heavy-fermion-like oxide LiV 2 O 4 is presented.
Jun Sugiyama - One of the best experts on this subject based on the ideXlab platform.
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dome shaped magnetic phase diagram of thermoelectric layered Cobaltites
APS, 2004Co-Authors: Jun Sugiyama, S Hebert, Jess H Brewer, E J Ansaldo, Hiroshi Itahara, Takao Tani, Masashi Mikami, Yusuke Mori, Takatomo Sasaki, A MaignanAbstract:Using muon spin spectroscopy we have found that, for both NaxCoO2 (0.6 ≤ x ≤ 0.9) and 3- and 4-layer Cobaltites, a common low temperature magnetic state (which in some cases is manifest as an incommensurate spin density wave) forms in the CoO2 planes. Here we summarize those results and report a dome-shaped relation between the transition temperature into the low-T magnetic state and the composition x for NaxCoO2 and/or the high-temperature asymptotic limit of thermopower in the more complex 3- and 4-layer Cobaltites. This behavior is explained using the Hubbard model on two-dimensional triangular lattice in the CoO2 plane.
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dome shaped magnetic phase diagram of thermoelectric layered Cobaltites
Physical Review Letters, 2004Co-Authors: Jun Sugiyama, S Hebert, Jess H Brewer, E J Ansaldo, Hiroshi Itahara, Takao Tani, Masashi Mikami, Yusuke Mori, Takatomo Sasaki, A MaignanAbstract:Using muon spin spectroscopy we have found that, for both Na x CoO 2 (0.6 ≤ x ≤ 0.9) and three- and four-layer Cobaltites, a common low temperature magnetic state (which in some cases is manifest as an incommensurate spin density wave) forms in the CoO 2 planes. Here we summarize those results and report an almost dome-shaped relation between the transition temperature into the low-T magnetic state and the composition x for Na x CoO 2 and/or the high-temperature asymptotic limit of thermopower in the more complex three- and four-layer Cobaltites. This behavior is explained using the Hubbard model on a two-dimensional triangular lattice in the CoO 2 plane.
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dome shaped magnetic phase diagram of thermoelectric layered Cobaltites
Physical Review Letters, 2004Co-Authors: Jun Sugiyama, S Hebert, Jess H Brewer, E J Ansaldo, Hiroshi Itahara, Takao Tani, Masashi Mikami, Yusuke Mori, Takatomo Sasaki, A MaignanAbstract:Using muon spin spectroscopy we have found that, for both ${\mathrm{N}\mathrm{a}}_{x}{\mathrm{C}\mathrm{o}\mathrm{O}}_{2}$ ($0.6\ensuremath{\le}x\ensuremath{\le}0.9$) and three- and four-layer Cobaltites, a common low temperature magnetic state (which in some cases is manifest as an incommensurate spin density wave) forms in the ${\mathrm{C}\mathrm{o}\mathrm{O}}_{2}$ planes. Here we summarize those results and report an almost dome-shaped relation between the transition temperature into the low-$T$ magnetic state and the composition $x$ for ${\mathrm{N}\mathrm{a}}_{x}{\mathrm{C}\mathrm{o}\mathrm{O}}_{2}$ and/or the high-temperature asymptotic limit of thermopower in the more complex three- and four-layer Cobaltites. This behavior is explained using the Hubbard model on a two-dimensional triangular lattice in the ${\mathrm{C}\mathrm{o}\mathrm{O}}_{2}$ plane.
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electronic structure of misfit layered calcium Cobaltite
Physical Review B, 2002Co-Authors: Ryoji Asahi, Jun Sugiyama, Toshihiko TaniAbstract:We have performed the first-principles calculations on (Ca 2 CoO 3 ) 4 (CoO 2 ) 6 to understand electronic structures of the misfit-layered calcium Cobaltite, (Ca 2 CoO 3 ) x CoO 2 , within the generalized gradient approximation.The optimized structure, consisting of a triple rocksalt-type Ca 2 CoO 3 subsystem and a CdI 2 -type CoO 2 subsystem in which their respective octahedra are significantly distorted, shows good agreement with recent experiment. The calculated electronic structures include two-dimensionally dispersive e g bands across the Fermi energy, which yield the p-type conductivity in the rocksalt subsystem, while the Fermi energy lies in the crystal-field gap of the d states in the CoO 2 subsystem. The spin-polarized calculations show that antiferromagnetic or ferrimagnetic ordering with a small net magnetic moment within the rocksalt subsystem is found to be the ground state, which gives a reasonable explanation of low-temperature behavior of the resistivity and the susceptibility observed in experiment.