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Register a new userHybridized magnetic microwire metacomposites towards microwave cloaking and barcoding applications
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The microwave behavior of polymer metacomposites containing parallel Fe-based and continuous/short-cut Co-based microwire arrays has been investigated. A magnetic field-tunable metacomposite feature has been identified in the dense continuous hybrid composite confirmed by the transmission windows in the frequency band of 1 to 3.5 GHz. The complex magnetically tuned redshift-blueshift evolution of the transmission window is reasoned to result from the competition between the dynamic wire-wire interaction and the ferromagnetic resonance of Fe-based wires. Increasing Co-based inter-wire spacing to 10 mm in the continuous hybrid composites, a remarkable dual-band transmission window in the 1.5-3.5 GHz and 9-17 GHz is respectively induced by the ferromagnetic resonance of Fe-based wires and the magnetic resonance arising between Fe-Co wire couples. The hybridization of parallel Fe-based and short-cut Co-based wires in the polymer composite leads to a significant enhancement of the transmission window in the frequency band of 1 to 6 GHz due to the band-stop nature of Co-based wires. The advanced hybridized microwire metacomposites are arguably demonstrated to be particularly attractive for microwave cloaking and radio frequency barcoding applications.
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Traditional approaches to realize microwave tunability in microwire polymer composites which mainly rely on topological factors, magnetic field/stress stimuli, and hybridization prove to be burdensome and restricted to rather narrow band frequencies. This work presents a novel yet facile strategy based on a single component tunable medium to program the transmission response over wide frequency bands. To this end, we demonstrated that structural modification of one type of microwire through suitable current annealing and arrangement of the annealed wires in multiple combinations were sufficient to distinctly red-shift the transmission dip frequency of the composites. Such one wire control-strategy endorsed a programmable multivariable system grounded on the variations in both the overall array conductivity or effectiv area determined by the wires arrangement and the relaxation time dictated by the annealing degree of microwires. These results can be used to prescribe transmission frequency bands of desired features via diverse microwire arrays and microwave performance from a single component to a composite system design.
We investigated the microwave properties of polymer based metacomposites containing hybridized parallel Fe- and Co-based microwire arrays. A dual-band left-handed feature was observed in the frequency bands of 1.5 to 5.5 GHz and 9 to 17 GHz, indicated by two transmission windows associated with ferromagnetic resonance of Fe-based microwires and long range dipolar resonance between the wire arrays. The plasma frequency after hybridization is significantly increased due to the enhanced effective diameter through the wire-wire interactions between the Fe- and Co- microwire couples. These results offer essential perspectives in designing the multi-band metamaterial for microwave applications such as sensors and cloaking devices.
We report measurements of the low temperature (T = 0.5 K) oscillatory magnetization in a high-density array of 50 micron diameter wires of polycrystalline Bi utilizing a high sensitivity silicon cantilever magnetometer. We find that the magnetic response is strongly anisotropic, being much larger for magnetic field perpendicular than for fields parallel to the wire-axis. We argue that this is a geometric effect caused by the large aspect ratio of the individual microwires in the array. The magnetic response of the microwires is dominated by the light electrons due to the larger cyclotron orbits in comparison with the heavier holes. We find that de Haas - van Alphen oscillations are easily resolved, and discuss the application of this technique to the study of Bi nanowire arrays.
The acoustic cloaking theory of Norris (2008) permits considerable freedom in choosing the transformation function f from physical to virtual space. The standard process for defining cloak materials is to first define f and then evaluate whether the materials are practically realizable. In this paper, this process is inverted by defining desirable material properties and then deriving the appropriate transformations which guarantee the cloaking effect. Transformations are derived which result in acoustic cloaks with special properties such as 1) constant density 2) constant radial stiffness 3) constant tangential stiffness 4) power-law density 5) power-law radial stiffness 6) power-law tangential stiffness 7) minimal elastic anisotropy.
Flexible magnetic devices, i.e., magnetic devices fabricated on flexible substrates, are very attractive in application of detecting magnetic field in arbitrary surface, non-contact actuators, and microwave devices due to the stretchable, biocompatible, light-weight, portable, and low cost properties. Flexible magnetic films are essential for the realization of various functionalities of flexible magnetic devices. To give a comprehensive understanding for flexible magnetic films and related devices, we have reviewed recent advances in the studies of flexible magnetic films including fabrication methods, magnetic and transport properties of flexible magnetic films, and their applications in magnetic sensors, actuators, and microwave devices. Three typical methods were introduced to prepare the flexible magnetic films. Stretching or bending the flexible magnetic films offers a good way to apply mechanical strain on magnetic films, so that magnetic anisotropy, exchanged bias, coercivity, and magnetoresistance can be effectively manipulated. Finally, a series of examples were shown to demonstrate the great potential of flexible magnetic films for future applications.
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