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>Quantitatively probing the magnetic behavior of individual nanoparticles by an AC field-modulated magnetic force microscopy
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Quantitatively probing the magnetic behavior of individual nanoparticles by an AC field-modulated magnetic force microscopy
Despite decades of advances in magnetic imaging, obtaining direct, quantitative information with nanometer scale spatial resolution remains an outstanding challenge. Current approaches, for example, Hall micromagnetometer and nitrogen-vacancy magnetometer, are limited by highly complex experimental apparatus and a dedicated sample preparation process. Here we present a new AC field-modulated magnetic force microscopy (MFM) and report the local and quantitative measurements of the magnetic information of individual magnetic nanoparticles (MNPs), which is one of the most iconic objects of nanomagnetism. This technique provides simultaneously a direct visualization of the magnetization process of the individual MNPs, with spatial resolution and magnetic sensitivity of about 4.8 nm and 1.85 × 10−20 A m2, respectively, enabling us to separately estimate the distributions of the dipolar fields and the local switching fields of individual MNPs. Moreover, we demonstrate that quantitative magnetization moment of individual MNPs can be routinely obtained using MFM signals. Therefore, it underscores the power of the AC field-modulated MFM for biological and biomedical applications of MNPs and opens up the possibility for directly and quantitatively probing the weak magnetic stray fields from nanoscale magnetic systems with superior spatial resolution.
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机译：尽管磁成像技术已经取得了数十年的进步，但获得具有纳米级空间分辨率的直接，定量信息仍然是一项艰巨的挑战。当前的方法，例如霍尔微磁力计和氮空位磁力计，受到高度复杂的实验设备和专用样品制备过程的限制。在这里，我们提出了一种新的交流场调制磁力显微镜（MFM），并报告了单个磁性纳米颗粒（MNP）的磁性信息的局部和定量测量，这是纳米磁性的最具标志性的对象之一。该技术同时提供了单个MNP磁化过程的直接可视化，其空间分辨率和磁灵敏度分别为4.8 nm和1.85×10 −20 A m 2 ，分别使我们能够分别估计单个MNP的偶极场和局部开关场的分布。此外，我们证明了使用MFM信号可以常规获得单个MNP的定量磁化矩。因此，它强调了交流场调制MFM在MNP的生物和生物医学应用中的强大功能，并开辟了直接和定量探测具有优越空间分辨率的纳米级磁性系统中的弱杂散磁场的可能性。
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