Magnetic field observations in CoFeB/Ta layers with 0.67-nm resolution by electron holography

Abstract

Nanometre-scale magnetic field distributions in materials such as those at oxide interfaces, in thin layers of spintronics devices, and at boundaries in magnets have become important research targets in materials science and applied physics. Electron holography has advantages in nanometric magnetic field observations, and the realization of aberration correctors has improved its spatial resolution. Here we show the subnanometre magnetic field observations inside a sample at 0.67-nm resolution achieved by an aberration-corrected 1.2-MV holography electron microscope with a pulse magnetization system. A magnetization reduction due to intermixing in a CoFeB/Ta multilayer is analyzed by observing magnetic field and electrostatic potential distributions simultaneously. Our results demonstrate that high-voltage electron holography can be widely applied to pin-point magnetization analysis with structural and composition information in physics, chemistry, and materials science.

Electron holography observation of electron spin polarization around charged insulating wire

“…The microstructure of various materials has been widely studied using transmission and analytical electron microscopy [ 1–10 ], and electric and magnetic fields both inside and outside materials have been investigated using Lorentz transmission electron microscopy [ 11 ], differential phase contrast scanning electron microscopy [ 12 , 13 ] and electron holography [ 14–24 ]. The magnetic flux distribution and domain structure of various magnetic materials have been successfully analyzed with these techniques.…”

In-Plane Magnetic Field Evaluation with 0.47-nm Resolution by Aberration-Corrected 1.2-MV Holography Electron Microscope

“…To realize high-resolution magnetic field observations, a pulse magnetization system was developed to reverse the magnetization in the sample without changing the geometrical configuration of the sample holder and stage referring to the electron beam. Using this system, the magnetic fields in CoFeB/Ta layers were observed at 0.67-nm resolution [3]. However, due to the experimental residual aberrations, the atomic-resolution has not been achieved.…”

Imaging vortex pinning and gyration by time-resolved and in-situ Lorentz microscopy

“…Electron holography allows direct access to the Aharonov-Bohm phase by interfering a reference wave with part of the wave that passed the magnetic object, using a biprism [60,[227][228][229]. Recently, it has been demonstrated that electron holography is capable of resolving magnetic field in a CoFeB/Ta multilayer sample with sub-1 nm resolution [42,230].…”

“…The study of the dynamics involved in the manipulation of nanoscale magnetic textures demands experimental methods with sufficient spatiotemporal resolution. Based on transmission electron microscopy (TEM), Lorentz microscopy [39][40][41] is an established method for the static imaging of nanoscopic magnetic structures, capable of resolving magnetic features < 1 nm [42]. While early attempts of time-resolved Lorentz microscopy do exist, these fell short in providing the spatial resolution achievable in static measurements [43,44].…”