Magnetic exchange force microscopy with atomic resolution
Magnetic exchange force microscopy with atomic resolution
复制标题
DOI：
10.1038/nature05617
复制
发表时间：
2007-03-29
期刊：
影响因子：
64.8
通讯作者：
Wiesendanger, Roland
中科院分区：
文献类型：
--
作者：
Kaiser, Uwe;Schwarz, Alexander;Wiesendanger, Roland
相邻原子磁矩（自旋）的排序导致了重要的集体现象，例如铁磁性和反铁磁性。因此，要充分了解纳米尺度的磁性，需要有关真实空间中自旋排列和原子分辨率的信息。自旋偏振扫描隧道显微镜可以实现这一点(1)，但只能探测导电材料。力显微镜可用于任何样品，与其电导率无关。特别是，磁力显微镜 (2) 非常适合探索铁磁畴结构。然而，无法实现原子分辨率，因为数据采集涉及尖端和样品之间的长程静磁力的感测。为了克服这一限制，人们提出了磁交换力显微镜(3)：通过使用带有磁性尖端的原子力显微镜(4)，应该可以检测尖端和样品自旋之间的短程磁交换力。在这里，我们展示了一种典型的反铁磁绝缘体，即氧化镍的（001）表面，磁交换力显微镜确实可以同时揭示表面原子及其自旋的排列。与之前实现该方法的尝试相反(5-8)，我们使用外部磁场来对准尖端顶点处的磁极化，以优化尖端和样品自旋之间的相互作用。这使我们能够观察彼此最接近的尖端原子和样品原子的自旋之间的直接磁交换耦合，从而证明磁交换力显微镜在原子水平上研究自旋间相互作用的潜力。
The ordering of neighbouring atomic magnetic moments ( spins) leads to important collective phenomena such as ferromagnetism and antiferromagnetism. A full understanding of magnetism on the nanometre scale therefore calls for information on the arrangement of spins in real space and with atomic resolution. Spin-polarized scanning tunnelling microscopy accomplishes this(1) but can probe only conducting materials. Force microscopy can be used on any sample independent of its conductivity. In particular, magnetic force microscopy(2) is well suited to exploring ferromagnetic domain structures. However, atomic resolution cannot be achieved because data acquisition involves the sensing of long-range magnetostatic forces between tip and sample. Magnetic exchange force microscopy has been proposed(3) for overcoming this limitation: by using an atomic force microscope(4) with a magnetic tip, it should be possible to detect the short-range magnetic exchange force between tip and sample spins. Here we show for a prototypical antiferromagnetic insulator, the ( 001) surface of nickel oxide, that magnetic exchange force microscopy can indeed reveal the arrangement of both surface atoms and their spins simultaneously. In contrast with previous attempts to implement this method(5-8), we use an external magnetic field to align the magnetic polarization at the tip apex so as to optimize the interaction between tip and sample spins. This allows us to observe the direct magnetic exchange coupling between the spins of the tip atom and sample atom that are closest to each other, and thereby demonstrate the potential of magnetic exchange force microscopy for investigations of inter-spin interactions at the atomic level.