Magnetic structure analyses of a material and its associated spin configurations are important issues not only in the fields of solid-state physics, inorganic chemistry, and spintronics but also in other fields such as materials science, engineering and electronics industries. The magnetic fine structure is generally determined by neutron scattering, X-ray magnetic circular dichroism, spin-polarized scanning tunneling microscopy, magnetic exchange force microscopy and electron microscopy. Among them, transmission electron microscopy (TEM) is a powerful tool capable of site-specific analysis of the magnetic structure inside materials. Development of hardware-type aberration correction in electron microscopy has enabled local structural observations with atomic resolution as well as chemical and vibration analysis. As for magnetic imaging, however, atomic-level spin configuration has been analyzed by electron energy-loss spectroscopy by placing samples in strong magnetic fields, which destroy the nature of the magnetic ordering in the samples. Although magnetic-field-free observation can visualize intrinsic magnetic fields of an antiferromagnet by unit-cell averaging, it is a challenge to directly observe the magnetic field of an individual atomic layer of a non-uniform structure.
We have developed a pulse-magnetization system, to extract the magnetic signal by separating it from non-uniform electrostatic (structural) signal. This system has enabled magnetic-field observation of local areas such as layers and nanomagnets at resolution of sub-nanometres [ 1]. However, there are additional problems to increase the resolution. The magnetic signal at atomic scale is weak; therefore, to increase signal-to-noise ratio, high-resolution magnetic-field observation requires relatively longer observation time than that of a strong electrostatic signal of atoms.