Effect of a Multilayer-Film Insulator on High-Frequency Loss.

The frequency dependence of complex permeability was investigatedin soft magnetic films. In order to obtain an excellent micro-magnetic core for the high-frequency range over 100 MHz, we measured the frequency dependence of the real and imaginary components of permeability (μ' and μ'') and the loss tangent (tan δ=μ''/μ') at 100 MHz. Multilayer films with a total magnetic film thickness of 1μm were fabricated by RF sputtering with ceramics of various thicknesses and at partial gas pressure. It was found that a high-frequency loss occurred in a micro-size (1×2 mm) multilayer film for CoFeSiB(0.1μm)/SiO2(0.05μm) and CoNbZr(0.1μm)/ZrO2(0.08μm). The present results emphasize that magnetic losses at high frequency should be taken into account in selecting an insulator for a multilayer magnetic core when we use magnetic film in a micro device for the high-frequency range.