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Abstract

The magnetic properties of the U-type ferrite synthesized by a sol-gel process had studied by substituting cobalt with manganese or zinc in cobalt-based U-type ferrite. The substituted U-type ferrite showed a dominant crystal structure at a different substitution ratio of manganese and zinc. The change of the starting temperature of U-type ferrite formation according to substitutional elements was confirmed by TG-DTA analysis. In the case of manganese substitution, the starting temperature of U-type ferrite formation lowered, and on the contrary, when zinc was substituted, it became higher. The magnetic properties of the U-type ferrite substituted with manganese showed a tendency that the saturation magnetization was decreased and the coercivity was increased as the manganese ratio increased. The highest saturation magnetization was 57.9 emu/g in the specific composition (Ba4Co0.5Zn1.5Fe36O60) substituted with zinc.

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Authors and Affiliations

Kwang-Pil Jeong
Jeong-Gon Kim
Su-Won Yang
Jae-Ho Yun
Jin-Hyuk Choi
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Abstract

In this study, BaFe12-2xCoxTixO19 (X : 0 to 2.0, 0.2) powders were synthesized by sol-gel process. TG-DTA, XRD, SEM, VSM, and Network analyzer were measured in order to influence easy magnetization axis change on the wave absorption frequency range change. The easy magnetization axis change of the annealed powder at 900°C and 1200°C was confirmed by the coercive force decreased 4,800 and 3,870 Oe to 260 and 269 Oe, respectively, at the substitution ratio of 0.8 and 1.0. And it was confirmed that the change of the easy magnetization axis affected the change of the wave absorption frequency. The wave absorption frequency of substituted Barium Ferrite was less than 10 GHz range after the easy magnetization axis of Barium ferrite changed to a-b plan direction. It was confirmed the BaFe12-2xCoxTixO19(x = 0.8 to 1.6) was synthesized by the sol-gel process and it was annealed at 900°C and 1200°C, which could be used as a wave absorber in the X-band region of 10 GHz less.

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Authors and Affiliations

Su-Won Yang
Jeong-Gon Kim
Kwang-Pil Jeong
Han-Ul Shim
Seong-Il Cho
Min-Young Kim
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Abstract

In this study, the magnetic properties and wave absorption characteristics of high entropy alloys are investigated. The high entropy alloys with FeNiMnCoCu, FeNiMnZnCo, and FeNiZnCoCu compositions were synthesized by the sol-gel method. After the sol-gel process, the annealing process and hydrogen reduction process was performed. FeNiMnCoCu and FeNiZnCoCu were revealed soft magnetic property. The saturation magnetization was 12 emu/g and 36 emu/g, respectively. And The coercive force was –45 Oe and –34 Oe, respectively. The high entropy alloy with these compositions was revealed wave absorption property at above 10 gigahertz frequency region. And it has shown the trend that wave absorption frequency has decreased with the sample thickness increasing.

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Authors and Affiliations

Suwon Yang
Jeong-Gon Kim
Kwang-Pil Jeong
Jin-Hyuk Choi
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Abstract

The U-type ferrite is a kind of hexagonal ferrite, and it is known as a microwave absorber in the X-band. The magnetic and dielectric loss of the U-type ferrite change to the composition and coating layer, etc. In this study, the silicon oxide layer was coated on the substituted U-type ferrites to improve microwave absorption characteristics. The complex permittivity and complex permeability were measured using toroidal specimens that were press-molded and the measured frequency range was set from 2-18 GHz. The improvement of the microwave absorption rate was different according to the type of the substituted U-type ferrites. Only in the substituted U-type ferrites with nickel and zinc, an improvement in the microwave absorption rate due to enhancement of magnetic loss was confirmed. The highest microwave absorption was 99.9% at 9.6 GHz, which was S_Z0.5U.

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Authors and Affiliations

Kwang-Pil Jeong
Jeong-Gon Kim
Su-Won Yang
Jin-Hyuk Choi
Seung-Young Park

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