High frequency microwave characteristics of amorphous FeCoNiB–SiO2 thin films

Heusler Co2FeSi films with a uniaxial magnetic anisotropy and high ferromagnetic resonance frequency f r were deposited by an oblique sputtering technique on Ru underlayers with various thicknesses t Ru from 0 nm to 5 nm. It is revealed that the Ru underlayers reduce the grain size of Co2FeSi, dramatically enhance the magnetic anisotropy field H K induced by the internal stress from 242 Oe (1 Oe = 79.5775 A⋅m−1) to 582 Oe with an increment ratio of 2.4, while a low damping coefficient remains. The result of damping implies that the continuous interface between Ru and Co2FeSi induces a large in-plane anisotropic field without introducing additional external damping. As a result, excellent high-frequency soft magnetic properties with f r up to 6.69 GHz are achieved.

Section: Resultsmentioning

confidence: 99%

Improvement of high-frequency properties of Co₂FeSi Heusler films by ultrathin Ru underlayer*

Wang

Zhang

et al. 2020

“…Until now, microwave nano-absorbers, including nano-metals, nano-alloys, nanooxides, nano-conductive polymers, the composites of nanometals and insulation media and so on, have been extensively studied. [5][6][7][8][9][10] The potential microwave absorber with nanowire microstructure has a maximum absorption of 8.37 dB when the concentration of the ZnO nanowires is 6%. It has also been reported that the maximum absorption is enhanced up to 12.28 dB when the concentration of ZnO increases 7%.…”

Section: Introductionmentioning

confidence: 99%

“…[9] In particular, many efforts have been made to study the nanomaterials with the special microstructures. Qiu et al [10] reported that a cagelike ZnO/SiO 2 had been prepared, and the properties of microwave absorption had been studied. It has been found that the maximum absorption of the cagelike ZnO/SiO 2 is 10.68 dB at a frequency of 12.79 GHz, and the absorption range is from 10 GHz to 18 GHz under −6.0 dB.…”

Section: Introductionmentioning

confidence: 99%

Theoretical calculation and experiment of microwave electromagnetic property of Ni(C) nanocapsules

Zhang¹,

Hao²,

Zeng³

et al. 2016

With the combination of the dielectric loss of the carbon layer with the magnetic loss of the ferromagnetic metal core, carbon-coated nickel (Ni(C)) nanoparticles are expected to be the promising microwave absorbers. Microwave electromagnetic parameters and reflection loss in a frequency range of 2 GHz–18 GHz for paraffin-Ni(C) composites are investigated. The values of relative complex permittivity and permeability, the dielectric and magnetic loss tangent of paraffin-Ni(C) composites are measured, respectively, when the weight ratios of Ni(C) nanoparticles are equal to 10 wt%, 40 wt%, 50 wt%, 70 wt%, and 80 wt% in paraffin-Ni(C) composites. The results reveal that Ni(C) nanoparticles exhibit a peak of magnetic loss at about 13 GHz, suggesting that magnetic loss and a natural resonance could be found at that frequency. Based on the measured complex permittivity and permeability, the reflection losses of paraffin-Ni(C) composites with different weight ratios of Ni(C) nanoparticles and coating thickness values are simulated according to the transmission line theory. An excellent microwave absorption is obtained. To be proved by the experimental results, the reflection loss of composite with a coating thickness of 2 mm is measured by the Arch method. The results indicate that the maximum reflection loss reaches −26.73 dB at 12.7 GHz, and below −10 dB, the bandwidth is about 4 GHz. The fact that the measured absorption position is consistent with the calculated results suggests that a good electromagnetic match and a strong microwave absorption can be established in Ni(C) nanoparticles. The excellent Ni(C) microwave absorber is prepared by choosing an optimum layer number and the weight ratio of Ni(C) nanoparticles in paraffin-Ni(C) composites.

“…In pursuit of further miniaturization and higher frequency operation of magnetic devices such as magnetic recording heads, planar inductors, and sensors, the study of soft magnetic thin films is a persistent interest. The granular films prepared from ferromagnetic metals (for example, Fe, Co, Ni, and their alloys) and insulated oxides (SiO 2 , HfO 2 , and Al 2 O 3 ) [1][2][3] integrate high magnetic permeability µ, high electrical resistivity ρ (reducing the eddy loss), and moderate anisotropy field H k (determining the frequency range under which the electromagnetic devices can be operated). For the application requirements, the study of damping phenomena of the dynamic magnetization is critical for obtaining the optimum high-frequency magnetic properties and understanding the dynamic magnetization process in soft-magnetic films.…”

Section: Introductionmentioning

confidence: 99%

High frequency characteristics of (Ni ₇₅ Fe ₂ ) _x (ZnO) _{1−
x} granular thin films with tunable damping coefficient

Zuo

Xiao-hong

et al. 2015