Critical currents approaching the depairing limit at a twin boundary in YBa2CU3O7-delta

Article Abstract:

Research indicates that the twin boundary performs a key function in pinning vortices and improving the currents supported by the twinned orthorhombic crystals of YBaCU30y-delta while retaining superconductivity. Low spatial resolution can be studied via scanning tunnelling spectroscopy, with the superconducting order parameter probed at nonometre length scales. Use of this method shows that the perpendicular vortex flux over the boundary has a surprisingly large pinning strength, suggesting that the boundary-supported critical current is close to the theoretical 'depairing' limit.

Letter to the Editor, Flux pinning

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Novel field-induced asymmetry in the remanent magnetization of the superconductor YBa2Cu3O7

Article Abstract:

The oxide superconductor YBa2Cu3O7 contains an unexpected asymmetry in its magnetization profile, which results from the direction of the magnetic field. A scanning Hall microprobe detected the asymmetry while gauging the spatial and temporal changes in the superconductor's magnetic flux density. This asymmetry, caused by distortions to the magnetization profile due to the vortex's rotation, will force a reconsideration of current superconductivity theories none of which can explain this discovery.

Yttrium barium copper oxides

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Spin entropy as the likely source of enhanced thermopower in Na(sub)xCo(sub)2O(sub)4

Article Abstract:

Research shows that the electron-electron interaction may play a role in enhancing the thermopower of transition-metal-oxides and occurs via electronic spin entropy. Results indicate the complete suppression of entropy, in a magnetic field, in the layered oxide (sub)xCo(sub)2O(sub)4 as determined from thermopower and magnetization measurements. Data reveal that spin-entropy dominates the themopower enhancement in transition-metal oxides.

United States, Analysis, Influence, Magnetic fields, Thermal properties, Transition metal compounds, Electron-electron interactions, Entropy (Physics), Entropy (Thermodynamics), Chemical properties

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