Department of Basic and Applied Sciences for Engineering, SAPIENZA University of Rome, Rome, Italy.
Nanoscale. 2017 Nov 23;9(45):18000-18011. doi: 10.1039/c7nr05742c.
The development of high spatial resolution and element sensitive magnetic characterization techniques to quantitatively measure magnetic parameters of individual nanoparticles (NPs) and deeply understand and tune their magnetic properties is a hot topic in nanomagnetism. Magnetic force microscopy (MFM), thanks to its high lateral resolution, appears as a promising technique for the magnetic characterization of single nano-sized materials although it is still limited by some drawbacks, especially by the presence of electrostatic artifacts. Recently, these limitations have been overcome by the development of a particular MFM based technique called controlled magnetization - MFM (CM-MFM) allowing, in principle, a quantifiable correlation between the measured magnetic signal and the magnetization of the object under investigation. Here we propose an experimental procedure, based on the use of CM-MFM technique, to measure the magnetization curve of single magnetic NPs individuating their saturation magnetization, magnetic field, and coercivity. We measured, for the first time, the magnetization curves of individual FeO nanoparticles with diameters in the range of 18-32 nm by using a MFM instrument. Results are in very good agreement with the quantitative data obtained by SQUID analysis on a macroscopic sample, showing the high potential of the technique in the field of nanomagnetometry.
发展高空间分辨率和元素敏感的磁特性技术，以定量测量单个纳米粒子（NPs）的磁参数，并深入理解和调整其磁性能，是纳米磁学的一个热门话题。磁力显微镜（MFM）由于其高的横向分辨率，作为一种对单个纳米尺寸材料的磁特性进行表征的很有前途的技术出现，尽管它仍然受到一些缺点的限制，特别是存在静电伪影。最近，通过开发一种称为控制磁化-MFM（CM-MFM）的特殊 MFM 技术，克服了这些限制，该技术原则上允许在测量的磁信号和被研究物体的磁化之间进行可量化的关联。在这里，我们提出了一种基于使用 CM-MFM 技术的实验程序，以测量单个磁性 NPs 的磁化曲线，确定其饱和磁化强度、磁场和矫顽力。我们首次通过 MFM 仪器测量了直径在 18-32nm 范围内的单个 FeO 纳米粒子的磁化曲线。结果与宏观样品的 SQUID 分析获得的定量数据非常吻合，表明该技术在纳米磁计量领域具有很高的潜力。
