Sub-nanometer electron probes map magnetism at the nanoscale
J. Salafranca, J. Gazquez, N. Perez, A. Labarta, S. T. Pantelides, S. J. Pennycook, X. Batlle, M. Varela
For the first time, the electron microscope has been used to map the magnetization of nanoparticles in real space with sub-nanometer spatial resolution, along with their structure, chemistry and electronic properties. Research on magnetic materials has been long hampered by the lack of real space probes capable of looking at these systems with true sub-nanometer eyes. Studies, for example, of the magnetic properties of defects in a crystal, or the surface magnetism in interfaces or nanoparticles were as limited as our understanding of the underlying Physics. Electron magnetic chiral dichroism in the aberration corrected electron microscope, combined with density functional calculations, has shown that capping the surfaces with an organic acid restores magnetization on the surface layer1. The bonding with the acid’s O atoms results in O-Fe atomic configuration and distances close to the bulk values. We conclude that the nature and number of molecules in the capping layer is an essential ingredient in the fabrication of nanoparticles with optimal magnetic properties.