A millimeter-wave absorber based on gallium-substituted ε-iron oxide nanomagnets
A millimeter-wave absorber based on gallium-substituted ε-iron oxide nanomagnets
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DOI：
10.1002/anie.200703010
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发表时间：
2007-01-01
影响因子：
16.6
通讯作者：
Sasaki, Shinya
中科院分区：
文献类型：
--
作者：
Ohkoshi, Shin-ichi;Kuroki, Shiro;Sasaki, Shinya
毫米波范围内的电磁波（EM） （30 ~ 300ghz）正开始用于局域网和汽车间距离雷达等高速无线通信的电子设备中特别是频率为35,94和140 GHz的毫米波在空气中具有很高的透明度（所谓的空气窗口），对无线通信非常有用。互补金属氧化物半导体器件的发展也加速了这些波段电磁波的使用然而，目前在毫米波区域有效抑制电磁干扰（EMI）的材料几乎不存在因此，寻找合适的材料受到了很多关注。绝缘磁性材料由于铁磁共振而吸收电磁波。特别是，具有大矫顽力场（Hc）的磁性材料有望表现出高频共振。近年来，分离出了单相ε-Fe2O3纳米磁体。该纳米磁铁在室温下Hc值极高，可达20 kOe。[4-7]本文报道了一种由ε-GaxFe2ÀxO3 （0.10 x 0.67）纳米磁体组成的新型电磁吸收体，其在35-147 GHz区域表现出铁磁共振。此外，铁磁共振在x!处可以达到190 GHz左右频率的可能性。建议设置为0。通过结合反胶束和溶胶-凝胶技术或仅采用溶胶-凝胶法合成了一系列新的ε-GaxFe2ÀxO3 （0.10 x 0.67）纳米颗粒（见实验部分）。在样品的TEM图像中，对于x= 0.61，球形颗粒具有一定的粒径
Electromagnetic (EM) waves in the millimeter wave range (30–300 GHz) are beginning to be used in electronic devices for high-speed wireless communication such as in local-area networks and radars for the distance between cars.[1] Particularly, millimeter waves at frequencies of 35, 94, and 140 GHz have high transparency in the air (the so-called window of the air) and are useful for wireless communication. The development of complementary metal oxide semiconductor devices has also accelerated the use of EM waves in these bands.[2] However, currently materials that effectively restrain electromagnetic interference (EMI) in the region of millimeter waves almost do not exist.[3] Thus, finding a suitable material has received much attention. Insulating magnetic materials absorb EM waves owing to ferromagnetic resonance. Particularly, a magnetic material with a large coercive field (Hc) is expected to show a high-frequency resonance. In recent years, a single phase of ε-Fe2O3 nanomagnet has been isolated. This nanomagnet has an extremely large Hc value of 20 kOe at room temperature.[4–7] Herein, we report a new EM absorber composed of ε-GaxFe2ÀxO3 (0.10 x 0.67) nanomagnets, which shows a ferromagnetic resonance in the region of 35–147 GHz. In addition, the possibility that the ferromagnetic resonance can achieve a frequency of about 190 GHz at x! 0 is also suggested.A new series of ε-GaxFe2ÀxO3 (0.10 x 0.67) nanoparticles was synthesized by the combination of reversemicelle and sol–gel techniques or only the sol–gel method (see the Experimental Section). In the TEM image of the sample for x= 0.61, sphere-type particles with a particle size