Composition-controlled synthesis of solid-solution Fe-Ni nanoalloys and their application in screen-printed magnetic films

Screen printing is attracting attention as a method for manufacturing magnetic components such as on-chip transformers and inductors. Fe-Ni alloys, which have high saturation magnetizations and permeabilities, are suitable as magnetic materials for screen-printed high-frequency devices. Here, we demonstrate the fabrication of a screen-printed film comprising solid-solution Fe-Ni nanoalloys, which can achieve enhanced permeability and reduced eddy-current losses in high-frequency regions. The Fe-Ni nanoalloys were prepared by chemical reduction using sodium borohydride as a reducing reagent followed by hydrogen reduction. X-ray diffraction measurements, electron microscopy, and inductively coupled plasma spectroscopy revealed that well-mixed FexNi100-x nanoalloys (x=40, 21.5, and 10) with grain sizes of similar to 10nm were synthesized. The obtained nanoalloys showed high saturation magnetizations comparable to bulk alloys. The screen-printed film using the Fe21.5Ni78.5 nanoalloy exhibited the highest permeability of the nanoalloy films. The eddy-current loss was suppressed by the synthesis of nanoscale-grained nanoalloys. The permeability was sufficiently high for application in transformers and inductors.