91 research outputs found
Laparoscopic Wide Mesocolic Excision and Central Vascular Ligation for Carcinoma of the Colon
Peer reviewe
Magnetic interactions in the S = 1/2 square-lattice antiferromagnets Ba2CuTeO6 and Ba2CuWO6: parent phases of a possible spin liquid
The isostructural double perovskites Ba2CuTeO6 and Ba2CuWO6 are shown by theory and experiment to be frustrated square-lattice antiferromagnets with opposing dominant magnetic interactions. This is driven by differences in orbital hybridisation of Te6+ and W6+. A spin-liquid-like ground state is predicted for Ba2Cu(Te1-xWx)O6 solid solution similar to recent observations in Sr2Cu(Te1-xWx)O6
Tuning the square-lattice antiferromagnet SrCu(TeW)O from N\'eel order to quantum disorder to columnar order
The spin-1/2 square-lattice Heisenberg model is predicted to have a quantum
disordered ground state when magnetic frustration is maximized by competing
nearest-neighbor and next-nearest-neighbor interactions (). The double perovskites SrCuTeO and SrCuWO are
isostructural spin-1/2 square-lattice antiferromagnets with N\'eel (
dominates) and columnar ( dominates) magnetic order, respectively. Here we
characterize the full isostructural solid solution series
SrCu(TeW)O () tunable from N\'eel order to
quantum disorder to columnar order. A spin-liquid-like ground state was
previously observed for the = 0.5 phase, but we show that the magnetic
order is suppressed below 1.5 K in a much wider region of 0.1-0.6.
This coincides with significant -linear terms in the low-temperature
specific heat. However, density functional theory calculations predict most of
the materials are not in the highly frustrated region
square-lattice Heisenberg model. Thus, a combination of both magnetic
frustration and quenched disorder is the likely origin of the spin-liquid-like
state in = 0.5.Comment: 20+5 pages, 6+4 figures. Accepted for publication in PR
Structure, spin correlations and magnetism of the square-lattice antiferromagnet SrCuTeWO ()
Quantum spin liquids are highly entangled magnetic states with exotic
properties. The square-lattice Heisenberg model is one of the
foundational models in frustrated magnetism with a predicted, but never
observed, quantum spin liquid state. Isostructural double perovskites
SrCuTeO and SrCuWO are physical realizations of this model, but
have distinctly different types magnetic order and interactions due to a
effect. Long-range magnetic order is suppressed in the solid
solution SrCuTeWO in a wide region of , where
the ground state has been proposed to be a disorder-induced spin liquid. Here
we show that the spin-liquid-like and samples have
distinctly different local spin correlations, which suggests they have
different ground states. Furthermore, the previously ignored interlayer
coupling between the square-planes is likely to play a role in the suppression
of magnetic order on the W-rich side at . These results
highlight the complex magnetism of SrCuTeWO and hint at a
new quantum critical point at .Comment: 19+8 pages, 6+8 figure
Structure, Spin Correlations, and Magnetism of the S = 1/2 Square-Lattice Antiferromagnet Sr2CuTe1-xWxO6 (0 ≤ x ≤ 1)
Quantum spin liquids are highly entangled magnetic states with exotic properties. The S = 1/2 square-lattice Heisenberg model is one of the foundational models in frustrated magnetism with a predicted, but never observed, quantum spin liquid state. Isostructural double perovskites Sr2CuTeO6 and Sr2CuWO6 are physical realizations of this model but have distinctly different types of magnetic order and interactions due to a d10/d0 effect. Long-range magnetic order is suppressed in the solid solution Sr2CuTe1-xWxO6 in a wide region of x = 0.05-0.6, where the ground state has been proposed to be a disorder-induced spin liquid. Here, we present a comprehensive neutron scattering study of this system. We show using polarized neutron scattering that the spin liquid-like x = 0.2 and x = 0.5 samples have distinctly different local spin correlations, which suggests that they have different ground states. Low-temperature neutron diffraction measurements of the magnetically ordered W-rich samples reveal magnetic phase separation, which suggests that the previously ignored interlayer coupling between the square planes plays a role in the suppression of magnetic order at x ≈ 0.6. These results highlight the complex magnetism of Sr2CuTe1-xWxO6 and hint at a new quantum critical point between 0.2 < x < 0.4.</p
Structure, spin correlations, and magnetism of the S = 1/2 square-lattice antiferromagnet Sr2CuTe1–xWxO6 (0 ≤ x ≤ 1)
Quantum spin liquids are highly entangled magnetic states with exotic properties. The S = 1/2 square-lattice Heisenberg model is one of the foundational models in frustrated magnetism with a predicted, but never observed, quantum spin liquid state. Isostructural double perovskites Sr2CuTeO6 and Sr2CuWO6 are physical realizations of this model but have distinctly different types of magnetic order and interactions due to a d10/d0 effect. Long-range magnetic order is suppressed in the solid solution Sr2CuTe1–xWxO6 in a wide region of x = 0.05–0.6, where the ground state has been proposed to be a disorder-induced spin liquid. Here, we present a comprehensive neutron scattering study of this system. We show using polarized neutron scattering that the spin liquid-like x = 0.2 and x = 0.5 samples have distinctly different local spin correlations, which suggests that they have different ground states. Low-temperature neutron diffraction measurements of the magnetically ordered W-rich samples reveal magnetic phase separation, which suggests that the previously ignored interlayer coupling between the square planes plays a role in the suppression of magnetic order at x ≈ 0.6. These results highlight the complex magnetism of Sr2CuTe1–xWxO6 and hint at a new quantum critical point between 0.2 < x < 0.4
Conductivity and redox stability of new double perovskite oxide Sr 1.6 K 0.4 Fe 1+ x Mo 1− x O 6− δ (x= 0.2, 0.4, 0.6)
A series of new perovskite oxides Sr1.6K0.4Fe1+xMo1−xO6−δ (x = 0.2, 0.4, 0.6) were synthesised by solid state reaction method. Synthesis of Sr1.6K0.4Fe1+xMo1−xO6−δ (x = 0.2, 0.4, 0.6) was achieved above 700 °C in 5 % H2/Ar, albeit with the formation of impurity phases. Phase stability upon redox cycling was only observed for sample Sr1.6K0.4Fe1.4Mo0.6O6−δ. Redox cycling of Sr1.6K0.4Fe1+xMo1−xO6−δ (x = 0.2, 0.4, 0.6) demonstrates a strong dependence on high temperature reduction to achieve high conductivities. After the initial reduction at 1200 °C in 5 %H2/Ar, then re-oxidation in air at 700 °C and further reduction at 700 °C in 5 %H2/Ar, the attained conductivities were between 0.1 and 58.4 % of the initial conductivity after reduction 1200 °C in 5 %H2/Ar depending on the composition. In the investigated new oxides, sample Sr1.6K0.4Fe1.4Mo0.6O6−δ is most redox stable also retains reasonably high electrical conductivity, ~70 S/cm after reduction at 1200 °C and 2–3 S/cm after redox cycling at 700 °C, indicating it is a potential anode for SOFCs
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