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Three-Dimensional Magnetic Vortex Cores Visualized by Electron Holographic Vector Field Tomography

Spintronics, which uses electron spins, is expected to become a widely used device technology because it has advantages in terms of nonvolatility, data processing speed, electric power consumption, and integration densities compared with conventional semiconductor technologies. Since the functions of spintronics devices are controlled by changing the spin configuration, i.e., by changing the magnetic field vector distribution, their direct observation is important for understanding the mechanisms of spintronics devices. Vector field electron tomography (VFET) using a transmission electron microscope (TEM) is a powerful technique for visualizing three-dimensional (3D) magnetic vector distributions on the nanometer scale [1,2]. Here we report 3D magnetic vortices in stacked ferromagnetic discs in a nanoscale pillar using a 1 MV electron holography microscope and a dual-axis 360° rotation sample holder for the VFET [3].