Dual-axis 360° rotation specimen holder for analysis of three-dimensional magnetic structures

Abstract

A dual-axis 360° rotation specimen holder was developed for use in reconstructing the three-dimensional (3D) distribution of a magnetic field using a combination of electron holography and tomography. Pillar-shaped specimens are used to obtain accurate reconstruction without a missing angle. The holder's rotation rod can be turned >360°; the pillar is set ±45° to the azimuth for both x- and y-axis rotation. Two rotation series of holograms in individual axes are recorded for vector field tomography. The two vector components of the magnetic field are reconstructed directly from the two series of holograms, and the remaining component is calculated using Maxwell's equation, div B = 0. As a result, all 3D magnetic fields are reconstructed.

Higher-Order Structure of Human Chromosomes Observed by Electron Diffraction and Electron Tomography

“…Sufficient contrast was obtained in TEM images to observe 100-200 nm periodic structure although the chromosome was rather thick for a 300 keV TEM. The presence of the features was confirmed in a Hitachi 1 MeV TEM (Kawasaki et al, 2000a(Kawasaki et al, , 2000b, also equipped with a continuous 360°rotation TEM tomography holder (Tsuneta et al, 2014;Tanigaki et al, 2015). A tomography series consisting of 61 images was collected with a 3°tilt step (Hayashida & Malac, 2016;Hayashida et al, 2018) over the entire 0-180°tilt range at both microscopes.…”

“…Electron tomography (ET) in a TEM enables the visualization of the structure of an object in three dimensions (3D) at high spatial resolution. Using a dual beam-that is, a focused ion beam (FIB) instrument with an SEM column-an individual chromosome can be located and placed onto a 360°rotation ET sample holder then observed over a full tilt range (±90°) (Tsuneta et al, 2014;Tanigaki et al, 2015). The full tilt range ET allows us to overcome the loss of structural information due to the missing wedge of data and enables us to obtain a reconstruction of the chromosome that has isotropic resolution in 3D.…”

“…The use of 1 MeV of energy allows for the investigation of samples with a greater thickness than that allowed by the 300 keV microscope. In the same way as for the ED results, a chromosome extracted from a TEM grid using a dual beam instrument and placed onto a 360°continuous rotation holder (Yaguchi et al, 2008;Tsuneta et al, 2014;Tanigaki et al, 2015) also had 100-200 nm periodic features perpendicular to a chromosome axis. The ED and ET ability to detect periodicity of structure internal to an object, as opposed to on its surface, is an important advantage of ED and ET over SEM (Taniguchi & Takayama, 1986) and atomic force microscopy (Ushiki et al, 2002) of chromosomes.…”

Higher-order Structure of Human Chromosomes Observed by Electron Tomography and Electron Diffraction

“…Both samples were treated with ionic liquid [8]. For electron tomography, a chromosome from each sample was picked from the Carbon/Fomvar support film and transferred to a 360˚ rotation holder [9,10] using the method shown in Fig. 1 in HITACH NB5000 FIB/SEM to avoid a missing wedge effect [6].…”

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

“…The 1 MV holography electron microscope with high penetration power, which has been used to observe vortex behavior in high-Tc superconductors [4], is a promising instrument for observing practical spintronics devices because it does not require changing their inherent magnetic structures by sample thinning. The dual-axis 360º rotation sample holder can eliminate artifacts due to missing wedges while performing the VFET [5]. These electron microscopic technologies have been used to unveil 3D magnetic vortices in stacked ferromagnetic discs in a nanoscale pillar (Figure 1).…”