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低维普鲁士蓝类合物分子磁体与镍纳米线复合材料的制备与磁性研究

Preparation and Magnetic Properties of Low-dimensional Prussian Blue Analogue Molecular Magnet and Ni Nanowires Composite

【作者】 高波

【导师】 薛德胜;

【作者基本信息】 兰州大学 , 凝聚态物理, 2009, 博士

【摘要】 当前,纳米材料的新性质探索和新应用开发是纳米材料科学领域研究的前沿。我们以探索纳米材料的低维特性和高频应用为目的,制备了FeCrCr普鲁士蓝类合物分子磁体纳米线、MnFe普鲁士蓝类合物分子磁体纳米颗粒以及铁磁性金属Ni纳米线复合物,对其形貌、结构和磁性进行了研究,主要结论如下:1.利用氧化铝模板法制备了直径约为80nm的FeCrCr普鲁士蓝类合物纳米线阵列,该纳米线的研究结果表明:其晶体结构为面心立方结构,且存在Cr空位;红外光谱显示纳米线中离子的键合方式为FeⅡ-CN-CrⅢ和FenⅢ-CN-CrⅡ。2.通过对FeCrCr普鲁士蓝类合物纳米线的直流磁性和交流磁化率研究,发现在低温下存在负的磁化强度和自旋玻璃转变。分析认为铁磁性的Fe-Cr和反铁磁性的Cr-Cr对温度的依赖性不同导致产生了负的磁化强度,而结构中Cr空位的存在以及Fe-Cr与Cr-Cr之间铁磁与反铁磁相互作用的竞争是产生自旋玻璃态的原因。3.利用聚乙烯吡咯烷酮作为稳定剂合成了具有很好分散性的MnFe普鲁士蓝类合物纳米立方体颗粒,对该纳米颗粒的研究结果表明:其晶体结构为面心立方结构,且存在Fe空位;研究结果表明该纳米颗粒中离子的氧化态和键合方式为FeⅢ-CN-MnⅡ和FeⅡ-CN-MnⅢ。4.通过对MnFe普鲁士蓝类合物纳米颗粒的直流磁性和交流磁化率研究发现,该体系在低温下亦存在自旋玻璃转变,我们分析认为结构中存在的Fe空位使得MnFe普鲁士蓝类合物本来完整的有着长程相互作用的fcc结构,变成独立的然而仍然有弱相互作用的铁磁和反铁磁团簇。5.利用氧化铝模板法制备了线直径约为30nm的Ni纳米线以及Ni纳米线/石蜡复合物。对Ni纳米线的结构研究结果表明其晶体结构为面心立方结构。Ni纳米线的室温磁滞回线表明其形状各向异性使得其矫顽力较块体有所提高。6.通过对Ni纳米线/石蜡复合物在2-18GHz的磁谱与介电谱分析,发现该Ni纳米线复合物的高频趋肤效应被极大遏制,Ni纳米线的自然共振峰出现在10GHz左右。讨论了该复合物的微波性质,结果表明尽管与其他微波吸收体相比吸收性能并不是很理想,但是对于其微波吸收的机理探讨却是很有意义的。

【Abstract】 Recently, the low dimensional materials have attracted much attention for their distinctive properties and potential application. We synthesized FeCrCr Prussian Blue analogue nanowires and MnFe Prussian Blue analogue nanoparticles in order to investigate their low dimensional properties. We also synthesized Ni nanowires composite to develop microwave absorbing nanomaterials. The primary results are as follow:1. FeCrCr Prussian Blue analogue nanowires with diameters of about 80 nm have been synthesized with anodic oxide film template-based method. The structure analysis of the nanowires indicates a face centered structure. The elemental result indicates that the structure of the nanowires possess Cr vacancies. The infrared spectrum reveals that the oxidation states are FeⅡ-CN-CrⅢand FeⅢ-CN-CrⅡ.2. Dc and Ac magnetic properties of the FeCrCr Prussian Blue analogue nanowires are discussed. A negative magnetization and a low temperature spin glass behavior were observed. We consider that the negative magnetization is due to the different temperature dependent magnetization of the ferromagnetic Fe-Cr and anti-ferromagnetic Cr-Cr. The spin glass behavior is caused by the Cr vacancies in the structure and the competition of the ferromagnetic Fe-Cr and anti-ferromagnetic Cr-Cr.3. MnFe Prussian Blue analogue nanoparticles were synthesized by using polyvinyl pyrrolidone (PVP) as a protective matrix. The structure analysis of the nanoparticles indicates a face centered structure. The elemental result indicates that the structure of the nanoparticles possess Fe vacancies. The infrared spectrum and Mossbauer spectrum reveal that the oxidation states are FeⅡ-CN-MnⅢand FeⅢ-CN-MnⅡ.4. Dc and Ac magnetic properties of the MnFe Prussian Blue analogue nanoparticles are discussed. The infinite, percolating ferrimagnetic cluster expected for fcc lattice is broken into separate yet competing ferri-or antiferro-magnetic clusters due to the Fe vacancies which may be responsible for the low temperature spin glass behavior.5. In developing of the microwave absorbing material, we synthesized Ni nanowires/paraffin wax composite. The corresponding characterization, dc magnetication were reported. The complex permittivity and permeability properties of the Ni nanowires composite have been measured in the frequency range of 2-18 GHz. The resonance peak appeared at around 10 GHz in the permeability spectra. We found that the skin effect was suppressed in the composite, so the resonance peak was the consequence of the natural resonance resulted from the resonance absorption of the spin relaxation of magnetic moment in the Ni nanowires. The permeability spectra were fitted with the Landau-Lifshitz equation and the resonance frequency was calculated by Kittel formula. Our calculation results agree well with the experimental data.

  • 【网络出版投稿人】 兰州大学
  • 【网络出版年期】2011年 04期
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