High resistive nanocrystalline Fe-M-O (M=Hf, Zr, rare-earth metals) soft magnetic films for high-frequency applications (invited)

Abstract

Microstructure, soft magnetic properties, and applications of high resistive Fe-M-O (M=Hf, Zr, rare-earth metals) were studied. The Fe-M-O films are composed of bcc nanograins and amorphous phases with larger amounts of M and O elements which chemically combine each other. Consequently, the amorphous phases have high electrical resistivity. The compositional dependence of magnetic properties, electrical resistivity, and structure have been almost clarified. For example, the high magnetization of 1.3 T, high permeability of 1400 at 100 MHz and the high electrical resistivity of 4.1 μΩ m are simultaneously obtained for as-deposited Fe62Hf11O27 nanostructured film fabricated by rf reactive sputtering in a static magnetic field. Furthermore, Co addition to Fe-M-O films improves the frequency characteristics mainly by the increase in the crystalline anisotropy of the nanograins. The Co44.3Fe19.1Hf14.5O22.1 film exhibits the quality factor (Q=μ′/μ′′) of 61 and the μ′ of 170 at 100 MHz as well as the high Is of 1.1 T. This frequency characteristics is considered to be superior to the other films already reported. The films also exhibit high corrosion resistance in an isotonic sodium chloride solution. Therefore, these films enable us to realize the high-frequency magnetic devices, such as thin-film inductors and transformers for microswitching converters and ultrahigh-density recording heads.

Design of microfabricated inductors for microprocessor power delivery

“…Controlling this process to achieve desirable properties in terms of grain size, crystal phase, purity of metal grains, composition of the ceramic matrix, volume fraction of metal, and stress is difficult. Nonetheless, reactive sputtering has demonstrated that such a material can, in fact, have high performance at high frequencies, including relative permeability of 170 and É of 60 at 100 MHz, with permeability maintained to about 1 GHz [30], attractive properties for both power and RF applications. In [24], an inductor application of these materials in an efficient high-frequency dc-dc converter was demonstrated at low power density.…”

“…Although conventional powdered-metal materials have limited power performance at frequencies this high, recent work has shown that higher performance is possible in vacuum deposited materials with nanoscale particles of Co or Fe [27], [28], [29], [30]. These materials have been fabricated by reactive sputtering.…”

Fe/SiO2 Nanocomposite Soft Magnetic Materials

“…Meanwhile, the exchange coupling between neighboring magnetic nanoparticles can overcome the anisotropy and demagnetizing effects, resulting in better soft magnetic properties than conventional materials [I]. Based on this idea, nanocomposite thin films with significantly improved high frequency properties have been developed [2,3]. However, the thin film techniques cannot be used to produce bulk components.…”

Dynamic Magnetic Properties of Fe3O4 Nanoparticle Assembly in High-frequency Range

“…To investigate the applications in high-frequency devices, much research has been done on ferromagnetic material [1][2][3] . For practical applications using relative permeability, µr, such as suppression of randomly polarized electromagnetic wave noise and impedance control of circuits 2-dimensional-randomly arranged on a circuit board, magnetic materials with isotropic magnetic properties are required.…”