Application of soft magnetic amorphous alloy Fe80Nb6B14 as electromagnetic shields

Grzegorz Haneczok 2Ryszard Wroczyński 3Piotr Kwapuliński 2Artur Chrobak 1Zbigniew Stokłosa 2Józef Rasek 2

1. University of Silesia, Institute of Physics, Uniwersytecka 4, Katowice 40-007, Poland
2. University of Silesia, Institute of Material Science, Bankowa 12, Katowice 40-007, Poland
3. Wrocław University of Technology, Institute of Telecommunication and Acoustic, Wybrzeże St. Wyspiańskiego, Wrocław 50-370, Poland

Abstract

Soft magnetic properties of amorphous alloys based on iron can be improved by a thermal annealing at temperatures closed to the crystallization temperature. This is usually attributed to formation of nanocrystalline grains (αFe, αFe(Si)) embedded into amorphous matrix. For the Fe80Nb6B14 amorphous alloy the optimization effect was attributed to annealing out of free volume without formation of nanograins. Nb atoms cause a slowing down of diffusion processes which makes possible to obtain the relaxed amorphous phase. The optimization effect without formation of nanograins is very interesting because it can give very good soft magnetic material free of embrittlement.

The aim of the paper is to study the application of the Fe80Nb6B14 amorphous alloy as electromagnetic shields. The strips of as received material (thickness d=25 µm) were annealed at 700 K/1h. This optimization annealing gives material with initial magnetic permeability about 3x104 and coercive field less than 1 A/m. In order to study the shielding effectiveness single shields (25x25 cm2) were made of two layers of optimized amorphous strips. Each layer was glued onto one side of double-sided scotch tape. Every shield consists of more than 50 strips forming a uniform soft magnetic plane with thickness d=50 µm.

For magnetic field (impedance<377Ω) in frequency range 0.2-10000 kHz for a single shield b decreases from 15 to 5 dB. For a quadruple shield (d=200 µm) b>20 dB in frequency range 0.2-10 kHz. The shielding effectiveness for electric field (impedance>377Ω) decreases from 50 to 20 dB (2-15 MHz) independently of shield thickness. The best result was obtained for electromagnetic field (far zone, 200-1000 MHz). In this case for a single shield in all frequency range the shielding effectiveness is better than 30 dB. For a triple (d=150 µm) and quadruple (d=200 µm) shields b>100 dB.

 

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Presentation: poster at E-MRS Fall Meeting 2005, Symposium B, by Grzegorz Haneczok
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-20 05:44
Revised:   2009-06-07 00:44