Dielectric responses of the layered cobalt oxysulfide Sr2Cu2CoO2S2 with CoO2 square planes

Okada, Satoshi; Terasaki, Ichiro; Ooyama, H.; Matoba, Masanori

doi:10.1063/1.1689772

Cited by 9 publications

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References 12 publications

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“…27 Thus, the change in ρ(T ) and S(T ) at T * implies a modification of the electronic state of SrNbO 3.43 . Similar behaviors are also observed in the layered-cobalt oxysulfide Sr 2 Cu 2 CoO 2 S 2 , in which electronic inhomogeneity is proposed at about the temperature where the thermopower increases, 28 and in the Q1D oxide PrBa 2 Cu 4 O 8 , in which dimensional crossover is suggested. 29 Note that the thermopower along the c axis differs in magnitude from that reported in Ref.…”

Section: A Sample Characterization and Transport Propertiessupporting

confidence: 70%

Anisotropic thermoelectric properties associated with dimensional crossover in quasi-one-dimensional SrNbO3.4+d(d∼0.03)

et al. 2011

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Section: A Sample Characterization and Transport Propertiessupporting

confidence: 70%

Anisotropic thermoelectric properties associated with dimensional crossover in quasi-one-dimensional SrNbO3.4+d(d∼0.03)

et al. 2011

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“…13 Sr 2 CoO 2 Cu 2 S 2 was also reported to show semiconducting behavior, while the resistivity of the Ba analogue is 10 4 times higher. 2 Subsequent investigations of the dielectric response and the transport properties of sintered powders of Sr 2 CoO 2 Cu 2 S 2 12 seem to suggest a possible spin-carrier phase separation below T N : electron transfer from the S 3p-based states at the top of the valence band onto Co results in mobile holes in the chalcogenide layer and an insulator-to-metal transition on cooling. However, there is no clear consensus in the literature as to the nature of the behavior of Sr 2 CoO 2 Cu 2 S 2 .…”

Section: ' Introductionmentioning

confidence: 99%

High-Spin Cobalt(II) Ions in Square Planar Coordination: Structures and Magnetism of the Oxysulfides Sr₂CoO₂Cu₂S₂ and Ba₂CoO₂Cu₂S₂ and Their Solid Solution

et al. 2011

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The antiferromagnetic structures of the layered oxychalcogenides (Sr(1-x)Ba(x))(2)CoO(2)Cu(2)S(2) (0 ≤ x ≤ 1) have been determined by powder neutron diffraction. In these compounds Co(2+) is coordinated by four oxide ions in a square plane and two sulfide ions at the apexes of an extremely tetragonally elongated octahedron; the polyhedra share oxide vertexes. The magnetic reflections present in the diffraction patterns can in all cases be indexed using a √2a × √2a × c expansion of the nuclear cell, and nearest-neighbor Co(2+) moments couple antiferromagnetically within the CoO(2) planes. The ordered magnetic moment of Co(2+) in Sr(2)CoO(2)Cu(2)S(2) (x = 0) is 3.8(1) μ(B) at 5 K, consistent with high-spin Co(2+) ions carrying three unpaired electrons and with an additional significant unquenched orbital component. Exposure of this compound to moist air is shown to result in copper deficiency and a decrease in the size of the ordered moment to about 2.5 μ(B); there is a strong correlation between the size of the long-range ordered moment and the occupancy of the Cu site. Both the tetragonal elongation of the CoO(4)S(2) polyhedron and the ordered moment in (Sr(1-x)Ba(x))(2)CoO(2)Cu(2)S(2) increase with increasing Ba content, and in Ba(2)CoO(2)Cu(2)S(2), which has Co(2+) in an environment that is close to purely square planar, the ordered moment of 4.5(1) μ(B) at 5 K is over 0.7 μ(B) larger than that in Sr(2)CoO(2)Cu(2)S(2), so the unquenched orbital component in this case is even larger than that observed in octahedral Co(2+) systems such as CoO. The experimental observations of antiferromagnetic ground states and the changes in properties resulting from replacement of Sr by Ba are supported by ab initio calculations on Sr(2)CoO(2)Cu(2)S(2) and Ba(2)CoO(2)Cu(2)S(2). The large orbital moments in these systems apparently result from spin-orbit mixing of the unequally populated d(xz), d(yz), and d(z(2)) orbitals, which are reckoned to be almost degenerate when the CoO(4)S(2) polyhedron reaches its maximum elongation. The magnitudes of the ordered moments in high-spin Co(2+) oxide, oxychalcogenide, and oxyhalide systems are shown to correlate well with the tetragonal elongation of the coordination environment. The large orbital moments lead to an apparently magnetostrictive distortion of the crystal structures below the Neél temperature, with the symmetry lowered from tetragonal I4/mmm to orthorhombic Immm and the size of the distortion correlating well with the size of the long-range ordered moment for all compositions and for temperature-dependent data gathered on Ba(2)CoO(2)Cu(2)S(2).

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“…The reported susceptibility measurements of Sr 2 MnO 2 Cu 2 S 2 11 suggest three-dimensional antiferromagnetic ordering of manganese moments. The semiconducting cobalt-containing analogue Sr 2 CoO 2 Cu 2 S 2 [14][15][16] also shows long-range antiferromagnetic ordering, but also more complex electronic behavior indicating a strong correlation between charge transport and the magnetic state 20 which has yet to be fully resolved. In contrast, the n ) 1; m ) 1 oxypnictides A 2 MnO 2 Zn 2 As 2 [21][22][23][24] are spin glasses with no long-range magnetic order.…”

Section: Introductionmentioning

confidence: 99%

Structural Chemistry and Metamagnetism of an Homologous Series of Layered Manganese Oxysulfides

et al. 2006

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An homologous series of layered oxysulfides Sr2MnO2Cu(2m-delta)S(m+1) with metamagnetic properties is described. Sr2MnO2Cu(2-delta)S2 (m = 1), Sr2MnO2Cu(4-delta)S3 (m = 2) and Sr2MnO2Cu(6-delta)S4 (m = 3), consist of MnO2 sheets separated from antifluorite-type copper sulfide layers of variable thickness by Sr(2+) ions. All three compounds show substantial and similar copper deficiencies (delta approximately equal to 0.5) in the copper sulfide layers, and single-crystal X-ray and powder neutron diffraction measurements show that the copper ions in the m = 2 and m = 3 compounds are crystallographically disordered, consistent with the possibility of high two-dimensional copper ion mobility. Magnetic susceptibility measurements show high-temperature Curie-Weiss behavior with magnetic moments consistent with high spin manganese ions which have been oxidized to the (2+delta)+ state in order to maintain a full Cu-3d/S-3p valence band, and the compounds are correspondingly p-type semiconductors with resistivities around 25 Omega cm at 295 K. Positive Weiss temperatures indicate net ferromagnetic interactions between moments. Accordingly, magnetic susceptibility measurements and low-temperature powder neutron diffraction measurements show that the moments within a MnO(2) sheet couple ferromagnetically and that weaker antiferromagnetic coupling between sheets leads to A-type antiferromagnets in zero applied magnetic field. Sr2MnO2Cu(5.5)S4 and Sr2MnO2Cu(3.5)S3 are metamagnets which may be driven into the fully ordered ferromagnetic state below 25 K by the application of fields of 0.06 and 1.3 T respectively. The relationships between the compositions, structures, and physical properties of these compounds, and the prospects for chemical control of the properties, are discussed.

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Dielectric responses of the layered cobalt oxysulfide Sr2Cu2CoO2S2 with CoO2 square planes

Cited by 9 publications

References 12 publications

Anisotropic thermoelectric properties associated with dimensional crossover in quasi-one-dimensional SrNbO3.4+d(d∼0.03)

Anisotropic thermoelectric properties associated with dimensional crossover in quasi-one-dimensional SrNbO3.4+d(d∼0.03)

High-Spin Cobalt(II) Ions in Square Planar Coordination: Structures and Magnetism of the Oxysulfides Sr₂CoO₂Cu₂S₂ and Ba₂CoO₂Cu₂S₂ and Their Solid Solution

Structural Chemistry and Metamagnetism of an Homologous Series of Layered Manganese Oxysulfides

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Dielectric responses of the layered cobalt oxysulfide Sr2Cu2CoO2S2 with CoO2 square planes

Cited by 9 publications

References 12 publications

Anisotropic thermoelectric properties associated with dimensional crossover in quasi-one-dimensional SrNbO3.4+d(d∼0.03)

Anisotropic thermoelectric properties associated with dimensional crossover in quasi-one-dimensional SrNbO3.4+d(d∼0.03)

High-Spin Cobalt(II) Ions in Square Planar Coordination: Structures and Magnetism of the Oxysulfides Sr2CoO2Cu2S2 and Ba2CoO2Cu2S2 and Their Solid Solution

Structural Chemistry and Metamagnetism of an Homologous Series of Layered Manganese Oxysulfides

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High-Spin Cobalt(II) Ions in Square Planar Coordination: Structures and Magnetism of the Oxysulfides Sr₂CoO₂Cu₂S₂ and Ba₂CoO₂Cu₂S₂ and Their Solid Solution