Mapping spin structures on the atomic scale
R. Wiesendanger · Europhysics news · 2007
A fundamental understanding of magnetic and spin-depen- dent phenomena requires the determination of spin structures and spin excitations down to the atomic scale.The direct visualization of atomic-scale spin structures [1][2][3][4] has first been accomplished for magnetic metals by combining the atomic resolution capability of Scanning Tunnelling Microscopy (STM) [5,6] with spin sensitivity, based on vacuum tunnelling of spin-polarized electrons [7].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 [8].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 [9].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 SP-STM with inelastic electron tunnelling spectroscopy [10] or by performing MExFM together with high-precision measurements of damping forces [9] localized or confined spin excitations in magnetic systems of reduced dimensions now become experimentally accessible.