Composition Dependence of Magnetic Shielding Properties for Amorphous Ribbons (FeNi) 78 Mo 4 B 17 Si
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COMPOSITION DEPENDENCE OF MAGNETIC SHIELDING PROPERTIES FOR AMORPHOUS RIBBONS (FeNi)z8Moi+Bi 7 Si Der-Ray Huang, Wen-Huu Dow, Pei-Chih Yao and Shu-En Hsu Materials R&D Center, Chung Shan Institute of Science and Technology P. 0. Box 1-26, Lungtan, Taiwan 32500, R.0.C.
ABSTRACT Amorphous ribbons (FeNi) 78 Mo4 B1 7 Si, made by melt-spinning technique were prepared as magnetic shielding materials. Cylindrical shields (~O0.05mm thick) were fabricated by wrapping ribbons on 20cm long pyrex tubes with 45mm diameter. DC and AC (60Hz, 400Hz, 800Hz, 1 kHz) magnetic shielding data were obtained by following the modified ASTM (A698-74) procedure. For DC magnetic fields, Ni-rich shields showed maximum shielding values at lower applied fields (0.1I Oe-l Oe), while Fe-rich shields showed maximum shielding values at higher applied fields (I~50Oe). For AC magnetic fields, the magnetic fields, the magnetic shielding effectiveness was also influenced by skin effect at shields' surfaces. By comparing the data to calculations from shielding theory, there is about 8% magnetic shielding effectiveness induced by skin effect at 1 kHz.
INTRODUCTION For DC and low frequency magnetic shielding, a high permeability material is very effective for magnetic shielding. Because of their excellent soft magnetic and mechanical properties, iron-nickel base amorphous ribbons have been used as good magnetic shields in some electric devices. Amorphous ribbons (Fe 7 8 -xNix) Mo4Bl7Si with different concentration of Fe and Ni were investigated by measuring their magnetic, electric and magnetic shielding properties. The DC magnetic shielding effectiveness was primarily a function of shield's permeability, thickness and shape, while AC magnetic shielding effectiveness was affected not only by shunting effect, as for DC fields, but also by skin effect which induced an induction opposite the applied field.
EXPERIMENT Amorphous ribbons of the composition (Fe78_xNix) Mo4 Bi 7 Si (0
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