Nanocrystalline FeCoHf films with Hf composition gradient were prepared by gradient sputtering method at room temperature A uniaxial magnetic anisotropy with high anisotropy field Hk up to 547Oe was achieved after magnetic annealing with external field along the gradient direction Ultrahigh ferromagnetic resonance frequency over 7GHz was obtained in magnetic annealed gradient sputtered films The origin of ultrahigh ferromagnetic properties in gradient sputtered films is discussed

Ultrahigh-frequency ferromagnetic properties of FeCoHf films deposited by gradient sputtering

In this work, we realized in situ fabricated Co90Nb10 soft magnetic thin films, with variable in-plane uniaxial magnetic anisotropy, without using the field induced method or postfabrication treatment. In situ control over the in-plane uniaxial magnetic anisotropy field, which varied from 1.6to22.7kAm−1, was achieved by adjusting the deposition oblique angle from 0° to 38°. As a consequence, the resonance frequencies of the films were continuously increased from 1.3to4.9GHz.

In situ fabrication of Co90Nb10 soft magnetic thin films with adjustable resonance frequency from 1.3to4.9GHz

Excellent soft magnetic properties have been achieved in a wide metal volume fraction (x) range for as-deposited (Fe65Co35)x(SiO2)1?x granular films fabricated by magnetron sputtering. With the decrease in x from 0.7 to 0.5, the films exhibit small coercivity Hc not exceeding 4?Oe and high electrical resistivity ? up to 5.48 ? 103????cm. A minimum Hc value of 1.7?Oe was obtained for the sample of x = 0.57 with ? = 2.86 ? 103????cm. At a frequency lower than 1.3?GHz, the real part ?' of complex permeability of this sample is about 170 and then decreases with frequency while the imaginary part ?'' is visible when f > 1?GHz, which may be caused by anisotropy dispersion. The FMR frequency is as high as 2.4?GHz, implying a high cut-off frequency for high frequency applications. A study of high resolution transmission electronic microscope indicates that the samples consist of Fe65Co35 particles uniformly embedded in an insulating SiO2 matrix. The excellent soft magnetic property is ascribed to exchange coupling among magnetic particles. The investigation of the ?m?H curve evidences the existence of this inter-granule interaction.

http://iopscience.iop.org/article/10.1088/0022-3727/40/12/016/pdf

Microstructure and magnetism of FeCo?SiO2 nano-granular films for high frequency application

On-chip metal inductors that revolutionized radio frequency electronics in the 1990s suffer from an inherent limitation in their scalability in state-of-the-art radio frequency integrated circuits. This is because the inductance density values for conventional metal inductors, which result from magnetic inductance alone, are limited by the laws of electromagnetic induction. Here, we report inductors made of intercalated graphene that uniquely exploit the relatively large kinetic inductance and high conductivity of the material to achieve both small form-factors and high inductance values, a combination that has proved difficult to attain so far. Our two-turn spiral inductors based on bromine-intercalated multilayer graphene exhibit a 1.5-fold higher inductance density, leading to a one-third area reduction, compared to conventional inductors, while providing undiminished Q-factors of up to 12. This purely material-enabled technique provides an attractive solution to the longstanding scaling problem of on-chip inductors and opens an unconventional path for the development of ultra-compact wireless communication systems.

/pdf/on-chip-intercalated-graphene-inductors-for-next-generation-28akctvwix.pdf

On-chip intercalated-graphene inductors for next-generation radio frequency electronics

In this work, the static and high frequency magnetic properties of (Co90Nb10/Ta)(n) multilayers have been investigated. The results show that the in-plane uniaxial magnetic anisotropy fields can be adjusted from 12 to 520 Oe only by decreasing the thickness of Ta interlayers from 8.0 to 1.8 nm. As a consequence, the resonance frequencies of the multilayers continuously increased from 1.4 to 6.5 GHz. It was found that the changes in the in-plane uniaxial anisotropy field are ascribed to the interlayer interactions among the magnetic layers by investigating the delta M(H) curves.

Adjust the resonance frequency of (Co90Nb10/Ta)n multilayers from 1.4 to 6.5 GHz by controlling the thickness of Ta interlayers

The thin-film power amplifier module for wide-band code division multiple access was designed and fabricated using the magnetic thin film as magnetic core of choke inductors. CoFeSiO-SiO/sub 2/ multilayer granular films showing high resistivity and good magnetic properties were applied to the module. Inductance value increased about 30% by application of magnetic films, and occupation area and series resistance were also reduced by 20%. The obtained module size was 3.0 mm /spl times/ 3.5 mm, which was much smaller than the conventional power amplifier module, since the bias circuit was formed on the same silicon substrate.

R. Kondo

Papers

Thin-film inductor for gigahertz band with CoFeSiO-SiO/sub 2/ multilayer granular films and its application for power amplifier module