Magnetic nanocomposites (NCs) are extremely appealing for a wide range of energy-related technological applications, specifically as building blocks for next-generation permanent magnets. The design of such nanostructures requires precise chemical synthesis methods, which will permit the fine-tuning of the magnetic properties. Here we present an in-depth structural, morphological and magnetic characterization of ferrite-based nanostructures obtained through a bottom-up sol–gel approach. The combination of the high coercivity of a hard phase SrFe₁₂O₁₉ (SFO) and the high saturation magnetization of a soft phase, CoFe₂O₄ (CFO), allowed us to develop exchange-coupled bimagnetic NCs. A symbiotic effect is observed in a SFO/CFO nanocomposite, as the unique oriented growth of SFO prevents grain growth of the CFO, thus restricting the crystallite size of both. Through X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), and magnetic measurements we clarify the relationship between the distribution and size of hard/soft particles, the optimization of interfaces and the obtained uniform magnetic response. This study allowed us to establish the potentiality of hard/soft SFO/CFO nanostructures in current permanent magnet technology.

中文翻译：

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通过成分/相间耦合调节硬-软SrFe ₁₂ O ₁₉ / CoFe ₂ O ₄纳米结构的磁性能

磁性纳米复合材料（NCs）在与能源相关的广泛技术应用中具有极强的吸引力，特别是作为下一代永磁体的基础。这种纳米结构的设计需要精确的化学合成方法，这将允许磁特性的微调。在这里，我们介绍了通过自下而上的溶胶-凝胶方法获得的基于铁氧体的纳米结构的深入结构，形态和磁学表征。硬相SrFe ₁₂ O ₁₉（SFO）的高矫顽力和软相CoFe ₂ O ₄的高饱和磁化强度的结合（CFO），使我们能够开发交换耦合双磁NC。在SFO / CFO纳米复合材料中观察到共生效应，因为SFO的独特定向生长阻止了CFO的晶粒生长，从而限制了两者的微晶尺寸。通过X射线粉末衍射（XRPD），透射电子显微镜（TEM）和磁测量，我们弄清了硬/软颗粒的分布和尺寸，界面的优化以及所获得的均匀磁响应之间的关系。这项研究使我们能够确定当前永磁技术中硬/软SFO / CFO纳米结构的潜力。