Shape Anisotropy, Exchange‐Coupling Interaction and Microwave Absorption of Hard/Soft Nanocomposite Ferrite Microfibers
Shape Anisotropy, Exchange‐Coupling Interaction and Microwave Absorption of Hard/Soft Nanocomposite Ferrite Microfibers
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DOI：
10.1111/j.1551-2916.2012.05375.x
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发表时间：
2012-12
影响因子：
3.9
通讯作者：
Xiang‐qian Shen;Fu-zhan Song;Jun Xiang;Mingquan Liu;Y. Zhu;Yingde Wang
中科院分区：
文献类型：
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作者：
Xiang‐qian Shen;Fu-zhan Song;Jun Xiang;Mingquan Liu;Y. Zhu;Yingde Wang
采用凝胶前驱体转化法制备了BaFe_（12）O_（19）（BFO）/Ni_（0.5）Zn_（0.5）Fe_2 O_4（NZFO）纳米复合取向微纤维，纤维直径为0.8 ~ 2 μm，长径比为0.8 ~ 2 μm，BFO为硬磁相，NZFO为软磁相。凝胶前驱体在1000°C下煅烧3 h后形成纳米复合二元铁氧体。这些纳米复合材料排列的微纤维表现出明显的形状各向异性。它们在297和77 K下的磁性差异主要来自于交换耦合作用和热涨落对偶极作用的竞争。结果表明，BFO/NZFO的质量比和试样厚度对复合材料的吸波性能有很大的影响。当BFO：NZFO质量比为7：3，样品厚度为3 mm时，在12.4 GHz处的最小反射损耗（RL）达到了-35.5 dB，具有9.1 ~ 15.7 GHz的宽吸收带宽（RL值超过-20 dB），覆盖了80%的X波段（8.2-12.4 GHz）和59%的Ku波段（12.4-18.0 GHz）。这种微波吸收的改善可以归因于纳米复合微纤维中的交换耦合相互作用、形状各向异性、界面极化和小尺寸效应。
The nanocomposite BaFe12O19 (BFO)/Ni0.5Zn0.5Fe2O4 (NZFO)-aligned microfibers with diameters 0.8–2 μm and high aspect ratios have been prepared by the gel precursor transformation process, where BFO is the hard magnetic phase and NZFO the soft magnetic phase. The nanocomposite binary ferrites are formed after the gel precursor calcined at 1000°C for 3 h. These nanocomposite aligned microfibers exhibit a clear shape anisotropy. Their magnetic difference observed at 297 and 77 K largely arises from the competition of exchange-coupling interaction and thermal fluctuation on dipolar interaction. Consequently, their microwave absorption performance is largely influenced by the mass ratio of BFO/NZFO and specimen thickness. When the mass ratio (BFO:NZFO) is 7:3 and the specimen thickness is 3 mm, the minimum reflection loss (RL) reaches the optimized RL value of −35.5 dB at 12.4 GHz, with a wide absorption bandwidth (the RL value over −20 dB) from 9.1 to 15.7 GHz, which covers 80% of X-band (8.2–12.4 GHz) and 59% of Ku-band (12.4–18.0 GHz). This improvement in microwave absorption can be attributed to the exchange-coupling interaction, shape anisotropy, interfacial polarization, and small size effect in nanocomposite microfibers.