Abstract The magnetic domain state of carbon coated iron nanopowder (Fe@C) was studied by the internal field nuclear magnetic resonance (IFNMR) at 77 K using the spin echo technique. The structure and magnetic properties of the sample were further characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Mossbauer spectroscopy, vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA) and Raman Spectroscopy. The obtained IFNMR results of Fe@C powder were compared with that of micron sized carbonyl iron (CI) and electrolytic iron (EI) powders. The calculated critical size of the single domain iron particles in Fe@C is ∼ 16 nm. A higher enhancement in echo amplitude was observed due to better response of the domain walls of multidomain particles in comparison to the single domain particles. The echo signal of CI and EI particles exhibit a single narrow intense peak corresponding to the domain walls, whereas Fe@C exhibits two low amplitude peaks at two different frequencies: a low frequency (46.6 MHz) peak corresponds to the response of the domain walls of the multidomain particles and the other high frequency (47.2 MHz) signal (a shoulder) corresponding to the response of the magnetic nuclei inside the domain. Our results help in determining the domain state of iron-based magnetic particles using 57Fe-IFNMR.

中文翻译：

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通过 57 Fe 零外场核磁共振测定碳包覆铁纳米粒子的磁畴状态

摘要 使用自旋回波技术在 77 K 下通过内场核磁共振 (IFNMR) 研究了碳包覆铁纳米粉体 (Fe@C) 的磁畴状态。通过扫描电子显微镜(SEM)、X射线衍射(XRD)、穆斯堡尔光谱、振动样品磁强计(VSM)、热重分析(TGA)和拉曼光谱进一步表征了样品的结构和磁性。将获得的 Fe@C 粉末的 IFNMR 结果与微米级羰基铁 (CI) 和电解铁 (EI) 粉末的结果进行比较。Fe@C 中单畴铁粒子的计算临界尺寸为~16 nm。由于与单域粒子相比，多域粒子的畴壁响应更好，因此观察到回波幅度更高的增强。CI 和 EI 粒子的回波信号表现出与畴壁对应的单个狭窄的强峰，而 Fe@C 在两个不同频率处表现出两个低振幅峰：低频 (46.6 MHz) 峰对应于畴壁的响应多域粒子和其他高频 (47.2 MHz) 信号（肩部）对应于域内磁核的响应。我们的结果有助于使用 57Fe-IFNMR 确定铁基磁性颗粒的畴状态。2 MHz) 信号（肩峰）对应于域内磁核的响应。我们的结果有助于使用 57Fe-IFNMR 确定铁基磁性颗粒的畴状态。2 MHz) 信号（肩峰）对应于域内磁核的响应。我们的结果有助于使用 57Fe-IFNMR 确定铁基磁性颗粒的畴状态。