A sol-gel synthesis method was used for the synthesis of pure CoFeO (CFO) as well as Graphene Quantum Dots (GQDs) decorated CoFeO Hybrid Nanocomposite (GCHN). From X-ray diffraction (XRD) data it was analyzed that both these samples have a cubic structure with space group. Using Debye-Scherer's equation, the average sizes were determined to be 24.48 and 13.74 nm, respectively. FTIR spectra revealed details about vibration bands and functional groups present. Raman spectra confirmed existence of GQDs in GCHN with an I/I ratio of ∼0.8. The results of Field emission scanning electron microscopy (FESEM) analysis exhibited microstructural morphological details having shapes of grains to be non-uniform in shape. UV–visible data was used to calculate band gap (E) energy by using Tauc plot method and found to be 2.52 eV and 2.99 eV respectively for CFO and GCHN. Urbach energy (E) was found to be 1.03 and 1.19 eV for CFO and GCHN respectively. The dielectric properties of GCHN were analyzed for dependence on frequency and temperature and explained by Maxwell-Wagner-type polarization. The frequency-dependent ac conductivity (σ) followed Jonscher's power law and investigated dynamics of ion hopping. Impedance spectroscopy was used to further evaluate Nyquist plots with respect to temperature as well as magnetic fields to estimate grain and grain boundary contributions. This was further used to evaluate electrical characteristics such as relaxation time (τ). Activation energies (E) calculated using relaxation times were found to be 0.48 eV for CFO while 0.22 and 0.92 eV for GCHN respectively. At room temperature, CFO and GCHN exhibited a strong magneto-dielectric coupling (MD) and showed negative magneto-dielectric properties in low-frequency regions. At room temperature (RT), magnetization values of CFO and GCHN displayed were 38.48 and 7.52 emu/g respectively. The lower magnetization value was possibly due to shielding by GQDs in GCHN. These properties enable it to be used as a potential application in microelectronic systems, spintronics, optical and optoelectronic devices, magnetic resonance imaging (MRI) and memory devices.

中文翻译：

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CoFe2O4 和石墨烯量子点 (GQD) 装饰的 CoFe2O4 杂化纳米复合材料的合成、结构、光学、介电、磁性和磁介电性能

采用溶胶-凝胶合成方法合成了纯 CoFeO (CFO) 以及石墨烯量子点 (GQD) 装饰的 CoFeO 混合纳米复合材料 (GCHN)。从X射线衍射（XRD）数据分析，这两个样品都具有空间群的立方结构。使用 Debye-Scherer 方程，确定平均尺寸分​​别为 24.48 和 13.74 nm。 FTIR 光谱揭示了有关振动带和存在的官能团的详细信息。拉曼光谱证实了 GCHN 中 GQD 的存在，I/I 比约为 0.8。场发射扫描电子显微镜（FESEM）分析结果显示出晶粒形状不均匀的微观结构形态细节。利用紫外-可见光数据通过 Tauc 图法计算带隙 (E) 能量，发现 CFO 和 GCHN 的带隙 (E) 能量分别为 2.52 eV 和 2.99 eV。 CFO 和 GCHN 的 Urbach 能量 (E) 分别为 1.03 和 1.19 eV。分析了 GCHN 的介电特性对频率和温度的依赖性，并通过麦克斯韦-瓦格纳型极化进行了解释。频率相关的交流电导率 (σ) 遵循 Jonscher 幂律并研究了离子跳跃的动力学。阻抗谱用于进一步评估关于温度和磁场的奈奎斯特图，以估计晶粒和晶界的贡献。这进一步用于评估电气特性，例如弛豫时间 (τ)。使用弛豫时间计算出的活化能 (E) 对于 CFO 来说为 0.48 eV，而对于 GCHN 来说分别为 0.22 和 0.92 eV。在室温下，CFO和GCHN表现出强磁电耦合（MD），并在低频区域表现出负磁电特性。在室温（RT）下，CFO和GCHN显示的磁化强度值分别为38.48和7.52 emu/g。较低的磁化值可能是由于 GCHN 中 GQD 的屏蔽所致。这些特性使其能够在微电子系统、自旋电子学、光学和光电器件、磁共振成像 (MRI) 和存储器件中发挥潜在应用作用。