A fundamental understanding of magnetic and spin-dependent phenomena requires the determination of spin structures and spin excitations down to the atomic scale. The direct visualization of atomic-scale spin structures [1-4] has first been accomplished for magnetic metals by combining the atomic resolution capability of Scanning Tunnelling Microscopy (STM) with spin sensitivity, based on vacuum tunnelling of spin-polarized electrons [5]. The resulting technique, Spin-Polarized Scanning Tunnelling Microscopy (SP-STM), nowadays provides unprecedented insight into collinear and non-collinear spin structures at surfaces of magnetic nanostructures and has already led to the discovery of new types of magnetic order at the nanoscale [6]. More recently, the detection of spin-dependent exchange and correlation forces has allowed a first direct real-space observation of spin structures at surfaces of antiferromagnetic insulators [7]. This new type of scanning probe microscopy, called Magnetic Exchange Force Microscopy (MExFM), provides a powerful new tool to investigate different types of spin-spin interactions based on direct-, super-, or RKKY-type exchange down to the atomic level. By combining MExFM together with high-precision measurements of damping forces localized or confined spin excitations in magnetic systems now become experimentally accessible.
References:
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R. Wiesendanger et al., Europhys. Lett. 19, 141 (1992)
[2] S. Heinze et al., Science 288, 1805 (2000)
[3] A. Kubetzka et al., Phys. Rev. Lett. 94, 087204 (2005)
[4] M. Bode et al., Nature Materials 5, 477 (2006)
[5] R. Wiesendanger et al., Phys. Rev. Lett. 65, 247 (1990)
[6] K. von Bergmann et al., Phys. Rev. Lett. 96, 167203 (2006)
[7] U. Kaiser, A. Schwarz, and R. Wiesendanger, Nature (2007), in press
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