Magnetic Shielding Effectiveness of Iron-Based Amorphous Alloys and Nanocrystalline Composites

This paper refers to magnetic field shielding effectiveness Sh of the selected iron-based amorphous alloys and some magnetic composites. The measurement conditions were chosen regarding the potential sources such as energetic lines or electric devices. As it was shown, the shields made of amorphous and optimized (in amorphous phase) melt spun ribbons can be applied as highly efficient and flexible shields. In the group of the tested alloys, the highest S_H reveal (at H = 110 A/m and f = 55 Hz): Fe₈₄ Cr₂ B₁₄ (95%) and optimized Fe₇₂ Co₁₀ Nb₆ B₁₄ (97%) and Fe₈₀ Nb₆ B₁₄ (92%). In the case of the tested composites, a significant decrease of S_H was observed. The shielding effectiveness decreases with decreasing size of magnetic addition due to breaking magnetic flux circuit and dipolar interactions between particles. For the composite with magnetic flakes of 4 mm in diameter S_H is about 60%; therefore, it can be applied as coatings in order to fulfill human protective standards. For the composites with micro and nano-sized magnetic powder S_H does not depend of the composition which suggests that a response to a magnetic field is fully influenced by the demagnetization effect.