Visualizing electric/magnetic field distributions on an atomic scale
Differential Phase Contrast imaging (DPC)
Electric and magnetic fields can be visualized using the DPC-STEM method, which measures the small deflections of the electr on beam due to the fields inside the sample with segmented or pixelated detectors.
Observation of the magnetic field distribution (room temperature) of antiferromagnetic hematite at atomic resolution using DPC STEM.
The symmetry of the hematite crystal was used to remove the information about the electric field and the magnetic distribution was visualized by averaging over all unit cells. Colors indicate the direction and strength of the magnetic field.
Y. Kohno et. al, Nature 602, 234 (2022)
Reduction of diffraction contrast effects in DPC-STEM
Tilt-Scan system
The JEM-Z200MF is equipped with a dedicated beam deflection system making it possible to change the incidence angle of the electron beam. Acquiring multiple DPC STEM images at different incident angles and then superimposing the individual images reduces the effect of diffraction contrast as shown below. (tilt-scan averaged DPC STEM, tDPC-STEM).
Comparison of DPC TEM image of Nd2Fe14B with and without the use of the Tilt-Scan system.
These images were observed along the axis of easy magnetization. Arrows in images indicate domain wall positions.
Using the Tilt-Scan system diffraction contrast caused by precipitates is strongly reduced and the domain wall boundaries can be clearly observed.
Gallery: High resolution STEM
The combination of the magnetic field-free objective lens with a probe side Double corrector system enables atomic resolution STEM under magnetic field-free conditions. The large convergence angle mode enables STEM observation with a high spatial resolution on the order of 0.1 nm.
Neodymium Iron Boron magnet (Nd2Fe14B) High-resolution HAADF-STEM image taken along the [001] direction and corresponding FFT pattern. The displayed orange circle corresponds to information transfer at 1Å. The STEM image was formed by summing 30 drift-compensated images.
T. Seki et. al, Incommensurate grain-boundary atomic structure,
Nature Communications 14, 7806 (2023), Fig. 1
Gallery: High resolution TEM in HR mode
The HR mode enables TEM observations at higher magnification under magnetic field-free conditions. Combined with an image side spherical aberration corrector, atomic lattice resolved TEM images can be obtained.
High-resolution TEM images of magnetite nanoparticles (Fe3O4). By correcting the spherical aberration of the objective lens, the atomic arrangement of the magnetic particles can be studied.
Gallery: Bright and Dark Field TEM image in CV mode
Linking physical and magnetic structural features is made easy by JEM-Z200MF. In the CV mode, the diffraction plane aligns with the objective aperture plane, allowing for easy selection of diffraction features to generate bright field and dark field images of magnetic materials.
Bright-field and dark-field images of dislocations in a pure iron sample.
Dislocations were introduced by deforming the sample by 5% at liquid nitrogen temperature.
Yellow circles indicate the positions of the objective aperture. Incidence Direction: Near <001>
Data courtesy: Prof. Kazuto Arakawa, Shimane University
Gallery: Lorentz-TEM / Fresnel method
Using a TEM with a conventional objective lens, it is necessary to turn off the objective lens in order to observe magnetic domain structures. With JEM-Z200MF, magnetic domains are easily observed with the objective lens normally excited.
Under focused image / defocus value -800 μm
Observation of magnetic domains in a permalloy thin film (Fe22Ni78) using the Fresnel method. Black and white arrows indicate the positions of domain walls.
Fig. a Remanent state of the permalloy thin film
Fig. b-d Using the magnetic field generating coils, which surround the objective lens, an external magnetic field is applied along the Z-axis.
Sample courtesy: Dr. Takumi Sannomiya, Tokyo Institute of Technology