SOFT MAGNETIC-MATERIALS

Soft magnetic materials are central to nearly every aspect of modern electrical and electronics technology through their ability to concentrate and shape magnetic flux with great efficiency. The most important characteristics desired for essentially all soft magnetic applications are high saturation induction, high permeability, low coercivity, and low core loss. The state of the art in this field is reviewed with an emphasis on recent research results and with a view to identifying areas in which further development in materials and processing might lead to even better properties and greater application of novel technology. The advent of rapid solidification technology has made possible the most striking new materials, metallic glasses. The substitution of them for conventional materials has been demonstrated to reduce core loss in a wide variety of devices operating from dc to several MHz. Most line frequency magnetic applications are cost sensitive, so improved production and manufacturing engineering offer the most immediate prospects. At the other extreme, the availability of ferrites and metallic glasses with properties like higher B-H loop squareness and higher permeability and lower core loss at high frequency has made possible both new applications, such as sensors, and marked extension of old concepts. Examples of the latter include the use of magnetic amplifier regulation in switch-mode power supplies operating at up to 1 MHz and of magnetic pulse compression in devices controlling up to 1012 W. Fabrication and processing of devices using thin-film technology will likely extend use of soft materials to even more sophisticated applications. © 1990 IEEE