Composition Dependence of Magnetic Shielding Properties for Amorphous Ribbons (FeNi) 78 Mo 4 B 17 Si

Amorphous ribbons (FeNi) 78 Mo 4 B 17 Si, made by melt—spinning technique were prepared as magnetic shielding materials. Cylindrical shields (~0.05mm 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 (0.1 0e~l 0e), while Fe—rich shields showed maximum shielding values at higher applied fields (1~5 0e). For AC magnetic fields, the magnetic fields, the magnetic shielding effectiveness was also influenced by skin effect at shield' surfaces. By comparing the data to calculations from shielding theory, there is about 8% magnetic shielding effectiveness induced by skin effect at 1 kHz.