Microwave Metamaterials Containing Magnetically Soft Microwires
- PDF / 412,035 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 85 Downloads / 228 Views
Microwave Metamaterials Containing Magnetically Soft Microwires L. V. Panina1,2, M. Ipatov2, V. Zhukova2, J. Estevez2 and A. Zhukov2 1 School of Comp., Comm. and Electr., Univ. of Plymouth, Drake Circus, PL4 AA, Plymouth, UK. 2 Dpto. de Física de Materiales, Fac. Químicas, UPV/EHU San Sebastián 20009, Spain. ABSTRACT This paper discusses a new type of wire media based on amorphous ferromagnetic microwires. The combination of two effects, namely, a strong dispersion of the effective permittivity in metallic wire composites (resonance or plasmonic type) and giant magnetoimpedance effect in wires will result in unusual property that an effective dielectric response may strongly depend on the wire magnetization which can be changed with different external stimuli. We have demonstrated the effect of the external magnetic field on microwave response from composites containing CoFeSiBCr amorphous wires in free space at microwave frequency. INTRODUCTION Composites with embedded metallic wires may demonstrate a strong dispersion of the effective permittivity İef in the microwave range [1-4]. This dispersion depends on the impedance of the wires that gives the possibility to sensitively tune the dispersion by changing the impedance of the wires. The possibility to control or monitor electromagnetic permittivity (and therefore scattering and absorption) is important for many applications such as remote nondestructive testing, structural health monitoring, tuneable coatings and absorbers. In our approach we use the ferromagnetic wires with high magnetoimpedance (MI) effect to control the electromagnetic permittivity (and therefore scattering and absorption) of composite metamaterials by changing the magnetic properties of embedded microwires with external stimuli (magnetic field, current, stress, temperature). The high frequency impedance of a soft magnetic conductor may experience enormous changes when its static magnetic structure undergoes transformation due to application of a magnetic field, stress or temperature. This effect is intrinsically related to magnetic softness and requires low magnetic anisotropy constant and high circumferential magnetic permeability. In particular, these conditions are fulfilled in magnetically soft amorphous microwires with low and negative magnetostriction constant (Ȝs § í10í7) where GMI effect reaching several hundred percents is often observed. The characteristic magnetic fields required to cause this impedance change could be quite small, in the range of few Oe. In this paper we have discussed the development of metamaterials with arrays of continuous wires and of short-cut ferromagnetic microwires, exploiting unique magnetic properties of wires to tune the effective electromagnetic parameters in the microwave frequency band. We made the measurements of the impedance in a single wire as a function of the external dc field at microwave frequencies, and free space measurements of reflection/transmission spectra with extracting the effective parameters. We have demonstrated that the applicat
Data Loading...
