This paper presents a new electromagnetic functional material developed byelectron-less nickel deposition technique, with a single hollow micro-sphere as the core templateand a thin nickel layer as the shell. The micr...This paper presents a new electromagnetic functional material developed byelectron-less nickel deposition technique, with a single hollow micro-sphere as the core templateand a thin nickel layer as the shell. The micrograph taken by a scanning electron microscope showsthe microstructures of the materials in detail. Scattering parameters of the waveguide sample holderfilled with the materials have been obtained over X band. The electromagnetic parameters computedfrom the measured S parameters show that the material with metallic hollow spheres has as highrelative permeability μ'_r as 19.0 with about 0.6 magnetic loss tangent over the whole bandwidth.Compared to the material with non-metallic spheres, the permeability μ'_r and the magnetic losstangent μ'_r increase greatly, while the permittivity remains lower than 1.8.展开更多
The coupled dynamic characteristics of the conical electromagnetic bearing are presented and their definitions are given. On the basis of the analyses of the characteristics, the dynamic model of five degrees of freed...The coupled dynamic characteristics of the conical electromagnetic bearing are presented and their definitions are given. On the basis of the analyses of the characteristics, the dynamic model of five degrees of freedom (five-DOF) rotor-conical electromagnetic bearing system is made, and the influence of the coupled characteristics on the system optimal controller is analyzed.展开更多
Two novel structures of fractal Cantor multilayer with defects are presented. The Optical transmission matrix method is used to calculate the transmittance and the reflectance. Compared with the general Cantor multila...Two novel structures of fractal Cantor multilayer with defects are presented. The Optical transmission matrix method is used to calculate the transmittance and the reflectance. Compared with the general Cantor multilayer, these novel structures have wider stopbands and show super narrow bands in the middle of the wider stopbands, which can be used as super narrow bandpass filters. The pass band can be less than 0.6 nm near the infrared wavelength of 1530 nm when there is an embedded defect in the cantor multilayer. The optical transmission in the central wavelength is higher than 99 %, which means a very low insert loss. If there are three layers, three super narrow peaks can be found in the middle of the stopband. The central wavelengths are respectively 1232.4 nm, 1372.8 nm and 1538.3 nm. It is much better than other kinds of narrow band filters and it may be used in the optical communications.展开更多
In this paper,we present a review of electron transport properties of magnetic granular films.Magnetic granular films are nanocomposite materials which consist of magnetic nanoparticles embedded in a nonmagnetic matri...In this paper,we present a review of electron transport properties of magnetic granular films.Magnetic granular films are nanocomposite materials which consist of magnetic nanoparticles embedded in a nonmagnetic matrix or assembling of magnetic nanoparticles.According to the style of the nonmagnetic matrix,microstructure and the electron transport mechanism of the films,the magnetic granular films were divided into three groups:(1) magnetic metal-metal granular films,(2) magnetic metal-insulator granular films and(3) magnetic nanocluster-assembled granular films.Moreover,we also systematically review the magnetic properties,transport properties and magnetoresistance effect of size-monodispersed Co and Fe nanocluster-assembled films.展开更多
The orbital magnetization of the electron gas on a two-dimensional kagome' lattice under a perpendicular magnetic field is theoretically investigated.The interplay between the lattice geometry and magnetic field i...The orbital magnetization of the electron gas on a two-dimensional kagome' lattice under a perpendicular magnetic field is theoretically investigated.The interplay between the lattice geometry and magnetic field induces nontrivial k-space Chern invariant in the magnetic Brillouin zone,which turns to result in profound effects on the magnetization properties.We show that the Berry-phase term in the magnetization gives a paramagnetic contribution,while the conventional term brought about by the magnetic response of the magnetic Bloch bands produces a diamagnetic contribution.As a result,the superposition of these two components gives rise to a delicate oscillatory structure in the magnetization curve when varying the electron filling factor.The relationship between this oscillatory behavior and the Hofstadter energy spectrum is revealed by selectively discussing the magnetization and its two components at the commensurate fluxes of f = 1/4,1/3,and 1/6,respectively.In particular,we reveal as a typical example the fractal structure in the magnetic oscillations by tuning the commensurate flux around f = 1/4.The finite-temperature effect on the magnetization is also discussed.展开更多
We have investigated the transport properties of the Dirac fermions through a ferromagnetic barrier junction on the surface of a strong topologicM insulator. The current-voltage characteristic curve and the tunneling ...We have investigated the transport properties of the Dirac fermions through a ferromagnetic barrier junction on the surface of a strong topologicM insulator. The current-voltage characteristic curve and the tunneling conductance are calculated theoretically. Two interesting transport features are predicted： observable negative differential conductances and linear conductances tunable from unit to nearly zero. These features can be magnetically manipulated simply by changing the spacial orientation of the magnetization. Our results may contribute to the development of high-speed switching and functional applications or electricalIy controlled magnetization switching.展开更多
文摘This paper presents a new electromagnetic functional material developed byelectron-less nickel deposition technique, with a single hollow micro-sphere as the core templateand a thin nickel layer as the shell. The micrograph taken by a scanning electron microscope showsthe microstructures of the materials in detail. Scattering parameters of the waveguide sample holderfilled with the materials have been obtained over X band. The electromagnetic parameters computedfrom the measured S parameters show that the material with metallic hollow spheres has as highrelative permeability μ'_r as 19.0 with about 0.6 magnetic loss tangent over the whole bandwidth.Compared to the material with non-metallic spheres, the permeability μ'_r and the magnetic losstangent μ'_r increase greatly, while the permittivity remains lower than 1.8.
文摘The coupled dynamic characteristics of the conical electromagnetic bearing are presented and their definitions are given. On the basis of the analyses of the characteristics, the dynamic model of five degrees of freedom (five-DOF) rotor-conical electromagnetic bearing system is made, and the influence of the coupled characteristics on the system optimal controller is analyzed.
基金This work was supported by National Science Foundation (60577 043)the Development Foundation of Shanghai Educational Committee (217608)Shanghai Leading Academic Discipline Project (T0102).
文摘Two novel structures of fractal Cantor multilayer with defects are presented. The Optical transmission matrix method is used to calculate the transmittance and the reflectance. Compared with the general Cantor multilayer, these novel structures have wider stopbands and show super narrow bands in the middle of the wider stopbands, which can be used as super narrow bandpass filters. The pass band can be less than 0.6 nm near the infrared wavelength of 1530 nm when there is an embedded defect in the cantor multilayer. The optical transmission in the central wavelength is higher than 99 %, which means a very low insert loss. If there are three layers, three super narrow peaks can be found in the middle of the stopband. The central wavelengths are respectively 1232.4 nm, 1372.8 nm and 1538.3 nm. It is much better than other kinds of narrow band filters and it may be used in the optical communications.
基金supported by the National Basic Research Program of China (Grant No. 2012CB933103)the National Science Fund for Distinguished Young Scholars (Grant No. 50825101)the National Natural Science Foundation of China (Grant Nos. 50971108 and 51171158)
文摘In this paper,we present a review of electron transport properties of magnetic granular films.Magnetic granular films are nanocomposite materials which consist of magnetic nanoparticles embedded in a nonmagnetic matrix or assembling of magnetic nanoparticles.According to the style of the nonmagnetic matrix,microstructure and the electron transport mechanism of the films,the magnetic granular films were divided into three groups:(1) magnetic metal-metal granular films,(2) magnetic metal-insulator granular films and(3) magnetic nanocluster-assembled granular films.Moreover,we also systematically review the magnetic properties,transport properties and magnetoresistance effect of size-monodispersed Co and Fe nanocluster-assembled films.
基金supported by the National Natural Science Foundation of China(Grant Nos.90921003,10904005,60776061 and 60776063)the National Basic Research Program of China(Grant Nos.2009CB929103 and 2009CB929300)
文摘The orbital magnetization of the electron gas on a two-dimensional kagome' lattice under a perpendicular magnetic field is theoretically investigated.The interplay between the lattice geometry and magnetic field induces nontrivial k-space Chern invariant in the magnetic Brillouin zone,which turns to result in profound effects on the magnetization properties.We show that the Berry-phase term in the magnetization gives a paramagnetic contribution,while the conventional term brought about by the magnetic response of the magnetic Bloch bands produces a diamagnetic contribution.As a result,the superposition of these two components gives rise to a delicate oscillatory structure in the magnetization curve when varying the electron filling factor.The relationship between this oscillatory behavior and the Hofstadter energy spectrum is revealed by selectively discussing the magnetization and its two components at the commensurate fluxes of f = 1/4,1/3,and 1/6,respectively.In particular,we reveal as a typical example the fractal structure in the magnetic oscillations by tuning the commensurate flux around f = 1/4.The finite-temperature effect on the magnetization is also discussed.
基金Supported by National Natural Science Foundation of China under Grant Nos.11174088,11175067,11274124
文摘We have investigated the transport properties of the Dirac fermions through a ferromagnetic barrier junction on the surface of a strong topologicM insulator. The current-voltage characteristic curve and the tunneling conductance are calculated theoretically. Two interesting transport features are predicted： observable negative differential conductances and linear conductances tunable from unit to nearly zero. These features can be magnetically manipulated simply by changing the spacial orientation of the magnetization. Our results may contribute to the development of high-speed switching and functional applications or electricalIy controlled magnetization switching.
