Effect of Si Addition on the Soft Magnetic Properties in High Frequency Range for Fe-Ni Alloy Powder

Abstract

Recently, soft magnetic metal powders are widely used for electric components such as inductors. These are required further improvement of magnetic properties. Fe-Ni soft magnetic alloys are called "Permalloy" and are known as high magnetic permeability alloys. In particular, "Permalloy B (JIS)", Fe-45~50Ni, is expected for application of inductors because of high saturation magnetic flux density. We researched the effect of Si addition into "Permalloy B" on the magnetic properties in high frequency range. Powders were prepared by gas atomization process and mixed with resin and lubricant, and then compacted into toroidal shape cores. These cores were heat-treated for hardening resin and release of internal stress by compaction. Effective permeability was measured by LCR meter up to 100 MHz and core loss was measured by B-H analyzer up to 5 MHz. As a result, permeability was slightly decreased but core loss was reduced by Si addition. Core loss was also reduced by using finer powders (mean particle diameters are less than 10 μm). Moreover, the permeability increased by the heat treatment of core after compaction. We found the availability of soft magnetic metal powders in high frequency over 3 MHz for using inductors.