Scanning Probe Microscopy for Spin Mapping and Spin Manipulation on the Atomic Scale

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 [6,7]. 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 [8]. This new type of scanning probe microscopy, called Magnetic Exchange Force Microscopy (MExFM), offers 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 with high-precision measurements of damping forces, localized or confined spin excitations in magnetic systems of reduced dimensions now become experimentally accessible. Moreover, the combination of spin state read-out and spin state manipulation, based on spin-current induced switching across a vacuum gap by means of SP-STM [9], provides a fascinating novel type of approach towards ultra-high density magnetic recording without the use of magnetic stray fields. \newline [1] R. Wiesendanger, I. V. Shvets, D. B\"{u}rgler, G. Tarrach, H.-J. G\"{u}ntherodt, J. M. D. Coey, and S. Gr\"{a}ser, Science \textbf{255}, 583 (1992) [2] S. Heinze, M. Bode, O. Pietzsch, A. Kubetzka, X. Nie, S. Bl\"{u}gel, and R.~Wiesendanger, Science \textbf{288}, 1805 (2000) [3] A. Kubetzka, P. Ferriani, M. Bode, S. Heinze, G. Bihlmayer, K. von Bergmann, O. Pietzsch, S. Bl\"{u}gel, and R. Wiesendanger, Phys. Rev. Lett. \textbf{94}, 087204 (2005) [4] M. Bode, E. Y. Vedmedenko, K. von Bergmann, A. Kubetzka, P. Ferriani, S. Heinze, and R. Wiesendanger, Nature Materials \textbf{5}, 477 (2006) [5] R. Wiesendanger, H.-J. G\"{u}ntherodt, G. G\"{u}ntherodt, R. J. Gambino, and R. Ruf, Phys. Rev. Lett. \textbf{65}, 247 (1990) [6] K. von Bergmann, S. Heinze, M. Bode, E. Y. Vedmedenko, G. Bihlmayer, S. Bl\"{u}gel, and R. Wiesendanger, Phys. Rev. Lett. \textbf{96}, 167203 (2006) [7] M. Bode, M. Heide, K. von Bergmann, P. Ferriani, S. Heinze, G. Bihlmayer, A. Kubetzka, O. Pietzsch, S. Bl\"{u}gel, and R. Wiesendanger, Nature \textbf{447}, 190 (2007) [8] U. Kaiser, A. Schwarz, and R. Wiesendanger, Nature \textbf{446}, 522 (2007) [9] S. Krause, L. Berbil-Bautista, G. Herzog, M. Bode, and R. Wiesendanger, Science \textbf{317}, 1537 (2007)