| 1. |
- Jiang, Wei, et al.
(författare)
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Static Magnetic Cloak without a Superconductor
- 2018
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Ingår i: Physical Review Applied. - : American Physical Society. - 2331-7019. ; 9:5
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Tidskriftsartikel (refereegranskat)abstract
- Similar to its electromagnetic counterpart, magnetic cloaking also has very important technological applications. However, the traditional method to build a static magnetic cloak requires the use of superconducting materials as the diamagnetic component, which seriously limits the practical potential because of the cryogenic condition. We show that a diamagnetic active current boundary combined with a high-permeability magnetic inner shell (MIS) can be designed to solve this problem, rendering an ideal magnetic cloaking effect at zero frequency. We first theoretically prove that a current boundary could magnetically behave as a superconductor to external observers. Based on this phenomena, we introduce a high-permeability MIS made of magnetically ultrasoft metallic sheets (permeability mu > 10(3)) and experimentally prove that the bilayer combination can exactly balance out the disturbance to the external probing field and, meanwhile, have a large invisible inner space. We also show that the active boundary currents can be accordingly configured to overcome the permeability and frequency band limits, leading to a robust cloak over the entire quasistatic frequency region. Our work creates an efficient way to circumvent the traditional limits of metamaterials to build magnetic cloaks for ultralow frequencies. The active-passive hybrid approach could be generally extended to yield other artificial magnetic devices or systems as well.
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| 2. |
- Man, Shahid, et al.
(författare)
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FeGaB(25 nm)/Al2O3/FeGaB(25 nm) Multilayer Structures : Effects of Variation of Al(2)O(3)Thickness on Static and Dynamic Magnetic Properties
- 2018
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Ingår i: Xiyou jinshu cailiao yu gongcheng. - : NORTHWEST INST NONFERROUS METAL RESEARCH. - 1002-185X. ; 47:7, s. 1951-1957
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Tidskriftsartikel (refereegranskat)abstract
- Iron-gallium (FeGa) thin film has the unique advantages in designing integrated magnetic sensors or chips due to its relatively large magnetostrictive constant compared with other soft magnetic materials. In this work, non-magnetic doping and laminating methods have been employed to control the magnetic and electric properties of this alloy film. By doping a certain amount of boron (B), the coercivities are largely decreased for samples of thickness less than similar to 30 nm. For thicker films, we find that inserting an ultrathin Al2O3 middle layer is very helpful to control the coercivities with negligible influence on saturation magnetization (M-s). The smallest easy-axis coercivity of 0.98x79.6 A/m is obtained in the multilayer film FeGaB(25 nm)/Al2O3(0.5 nm)/FeGaB(25 nm). In this case, the resistivity is enhanced by 1.5 times compared with the 50 nm single layer film. Structural characterizations indicate the reductions of crystalline quality and physical dimension of the magnetic grains playing important roles in softening the magnetic properties. Besides, the influences of magnetostatic interaction and morphology characteristics are also considered in facilitating domain reversal. High permeability spectra with gigahertz response are obtained for our multilayer films. The methodology applied here, i.e., enhancing magnetic and electric performance by introducing ultrathin non-magnetic layers, could be translated to other species of soft magnetic materials as well.
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