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163 results on '"Guo, Z.-b."'

4. Zonal Flow Patterns: How Toroidal Coupling Induces Phase Jumps and Shear Layers

Author

Guo, Z. B. and Diamond, P. H.

Subjects
Physics - Plasma Physics
Abstract

A new, frequency modulation mechanism for zonal flow pattern formation is presented. The model predicts the probability distribution function of the flow strength as well as the evolution of the characteristic spatial scale. Magnetic toroidicity-induced global phase dynamics is shown to determine the spatial structure of the flow. A key result is the observation that global phase patterning can lead to zonal flow formation in the absence of turbulence inhomogeneity., Comment: accepted by PRL

Published
2016
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6. Fabrication of graphene nanogap with crystallographically matching edges and its electron emission properties

Author

Wang, H. M., Zheng, Z., Wang, Y. Y., Qiu, J. J., Guo, Z. B., Shen, Z. X., and Yu, T.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

We demonstrate the fabrication of graphene nanogap with crystallographically matching edges on SiO2Si substrates by divulsion. The current-voltage measurement is then performed in a high-vacuum chamber for a graphene nanogap with few hundred nanometers separation. The parallel edges help to build uniform electrical field and allow us to perform electron emission study on individual graphene. It was found that current-voltage characteristics are governed by the space-charge-limited flow of current at low biases while the FN model fits the I-V curves in high voltage regime. We also examined electrostatic gating effect of the vacuum electronic device. Graphene nanogap with atomically parallel edges may open up opportunities for both fundamental and applied research of vacuum nanoelectronics., Comment: 12 pages,3 figures. to appear in APL

Published
2009
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9. Nonlocal phase coupling in turbulence spreading across the magnetic island.

Author

Zhang, Y., Jiang, M., Guo, Z. B., Xu, Y., Mao, Z. J., Hu, Z. Q., Xu, J. Q., Ke, R., Long, T., Wen, J., Yu, X., Li, J. Q., and Xu, M.

Subjects
TURBULENCE, CONVECTIVE flow, SHEAR flow, LAMINAR flow, ISLANDS, PLASMA turbulence
Abstract

We study the nonlocal phase coupling during turbulence spreading across the magnetic island. It is found that the coherent convective cells (sharing similar features to quasi-coherent mode in experiment) on both sides of the O-point boundary are accumulated during the island formation. The phase entrainment of the convective cells on the turbulence both in the inner and the outer regions of the magnetic island sets up a nonlocal phase coupling channel and leads to a fast spreading of the outer turbulence into the magnetic island by conquering the flow shear at the O-point boundary. This nonlocal coupling mechanism of turbulence spreading is analogous to a turbulence version of the well-known enhanced diffusion of passive scalars in laminar convective flows of neutral fluid system. [ABSTRACT FROM AUTHOR]

Published
2023
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24. Asymmetrically kinked hysteresis loops in exchange biased NiFe/IrMn rings.

Author

Guo, Z. B., Zheng, Y. K., Li, K. B., Liu, Z. Y., Luo, P., and Wu, Y. H.

Subjects
*HYSTERESIS, *MAGNETIC force microscopy, *TEMPERATURE, *FERROMAGNETIC materials, *ELECTROMAGNETIC induction, *MAGNETIZATION
Abstract

Magnetic properties of a series of NiFe/IrMn rings with inner diameters from 0.35 to 1.50 μm, while keeping the outer diameter of 2.0 μm, have been studied by magnetic force microscopy and hysteresis loop measurements at various temperatures. The enhancements in exchange bias and coercivity have been observed in the patterned ring structures. Asymmetrical, kinked hysteresis loops are present in the NiFe/IrMn rings with inner diameters less than 1.50 μm. The kinks in hysteresis loops in the increasing field branch correspond to the presence of a flux closure state. The presence of the flux closure state has been attributed to the formation of antiferromagnetic domain walls in the magnetization reversal which acts as an energy barrier and traps the flux closure state. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2004
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27. Structural and magnetoresistive properties of magnetic tunnel junctions with half-metallic Co2MnAl.

Author

Qiu, J. J., Han, G. C., Yeo, W. K., Luo, P., Guo, Z. B., and Osipowicz, T.

Abstract

A series of polycrystalline full-Heusler Co2MnAl thin films were deposited on Si (100) coated with thermo SiO2 by using different types of seed layers such as Cr, Mg, MgO/Cr, and MgO. The properties of the Co2MnAl thin films such as the coercivity, atomic composition, and crystalline structure strongly depend on the deposition conditions and seed layers. Very soft Co2MnAl thin films with coercivity of 8.3 Oe and small magnetostriction coefficient λS=1.43×10-5 had been obtained when MgO was used as seed layer. Magnetic tunnel junctions with magnetoresistance ratio of 12%–19% by utilizing the Co2MnAl as bottom ferromagnetic electrode have been successfully fabricated. [ABSTRACT FROM AUTHOR]

Published
2008
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28. Observation of a flux closure state in NiFe/IrMn exchange biased rings.

Author

Guo, Z. B., Zheng, Y. K., Li, K. B., Liu, Z. Y., Luo, P., Shen, Y. T., and Wu, Y. H.

Subjects
*HYSTERESIS loop, *MAGNETIZATION, *FERROMAGNETIC materials, *ANTIFERROMAGNETISM
Abstract

We have investigated the magnetic behaviors of the array of NiFe/IrMn rings, where a remarkably asymmetrical, kinked hysteresis loop has been observed in the sample. The kinked hysteresis loop has been attributed to the magnetization reversal, which starts from a single domain state to an opposite single domain state on one side of the loop, and takes place via the transition from a single domain state to a flux closure state and then into the opposite single domain state on the other side of the loop. This phenomenon is dramatically different from that of NiFe single layer rings. [ABSTRACT FROM AUTHOR]

Published
2003
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29. Low switching current flux-closed magnetoresistive random access memory.

Author

Zheng, Y. K., Wu, Y. H., Li, K. B., Qiu, J. J., Shen, Y. T., An, L. H., Guo, Z. B., Han, G. C., Luo, P., You, D., and Liu, Z. Y.

Subjects
MAGNETORESISTANCE, FERROMAGNETISM, MAGNETIZATION, RANDOM access memory
Abstract

A spin valve magnetoresistive random access memory with a flux-closed structure is presented. The flux-closed structure prevents the disruption to magnetization of the recording layer and increases the thermal stability. Simulation results show that the switching field increases under the uniform external field, however, the switching field has no change under the bit current field. Only the bit current that flows mostly at the center is used to switch the cell. Experimental results show that the bit current of 10 mA is sufficient to switch the 1 μm × 4 μm cell. [ABSTRACT FROM AUTHOR]

Published
2003
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32. Perpendicular magnetic anisotropy in Ta|Co40Fe40B20|MgAl2O4 structures and perpendicular CoFeB|MgAl2O4|CoFeB magnetic tunnel junction

Author

Tao, B. S., primary, Li, D. L., additional, Yuan, Z. H., additional, Liu, H. F., additional, Ali, S. S., additional, Feng, J. F., additional, Wei, H. X., additional, Han, X. F., additional, Liu, Y., additional, Zhao, Y. G., additional, Zhang, Q., additional, Guo, Z. B., additional, and Zhang, X. X., additional

Published
2014
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