Lorentz Microscopy and Electron Holography of Nanocrystalline Magnetic Materials

1999 ◽  
Vol 577 ◽  
Author(s):  
Marc De Graef
Keyword(s):  
Particle Size ◽  
Electron Holography ◽  
Beam Electron ◽  
Lorentz Microscopy ◽  
Size Limit ◽  
Model Image ◽  
Uniform Magnetization ◽  
Observation Method ◽  
Image Simulations ◽  
Lower Particle Size

ABSTRACTThis paper employs an analytical model for the phase shifts imparted on a beam electron by a spherical particle with a uniform magnetization. Model image simulations of Fresnel and Foucault type Lorentz microscopy contrast are presented. Estimates of a lower particle size limit for which no magnetic information can be extracted from the images are given and compared to similar estimates for the electron holography observation method. It is concluded that conventional Lorentz methods have a lower particle size limit of around 30 nm (for cobalt particles), while electron holography can be used to even smaller sizes.

Improved Lower Particle Size Limit for Aerosol Time-of-Flight Mass Spectrometry

2001 ◽  
Vol 34 (4) ◽  
pp. 381-385 ◽  
Author(s):  
Markus Gälli ◽  
Sergio A. Guazzotti ◽  
Kimberly A. Prather
Keyword(s):  
Mass Spectrometry ◽  
Particle Size ◽  
Time Of Flight ◽  
Size Limit ◽  
Flight Mass Spectrometry ◽  
Lower Particle Size

Phase Contrast Of Magnetic Cobalt Spheres

1999 ◽  
Vol 5 (S2) ◽  
pp. 34-35
Author(s):  
M. De Graef ◽  
N.T. Nuhfer ◽  
M.R. McCartney
Keyword(s):  
Detection Sensitivity ◽  
Electron Holography ◽  
Magnetic Vector Potential ◽  
Magnetic Recording Media ◽  
Lorentz Microscopy ◽  
Transmission Electron ◽  
Uniform Magnetization ◽  
Simple Model System ◽  
Experimental Resolution ◽  
Electron Microscopes

The recent increased interest in Lorentz Microscopy methods is due to two important factors: (1) the advent of digital detection systems (CCD cameras) and advanced computer controlled transmission electron microscopes, and (2) the continually decreasing length scale of magnetic recording media and related magnetic materials. Along with the increased experimental resolution and detection sensitivity one should ask the question: how small a magnetic moment can one detect with conventional Lorentz or electron holography techniques? And, perhaps more importantly, which technique should one use to obtain the best spatial resolution? To address these questions we identified a simple model system :the uniformly magnetized sphere.The phase of the electron wave after passing through a region with a non-zero magnetic vector potential and an internal electrostatic potential Vscan be computed from the Aharonov-Bohm trajectory integral. For a spherical particle with a uniform magnetization and a constant mean inner potential (see geometry in Fig. la), this phase shift can be analytically computed.

Real-time observation of vortex lattices in a superconductor

1993 ◽  
Vol 51 ◽  
pp. 1050-1051
Author(s):  
K. Harada ◽  
T. Matsuda ◽  
J.E. Bonevich ◽  
M. Igarashi ◽  
S. Kondo ◽  
...  
Keyword(s):  
Real Time ◽  
Flux Line ◽  
Electron Holography ◽  
Lorentz Microscopy ◽  
Vortex Lattices ◽  
Flux Lines ◽  
Magnetic Flux Lines ◽  
Time Observation ◽  
Thin Superconductor ◽  
Real Time Observation

Previous observations of magnetic flux-lines (vortex lattices) in superconductors, such as the field distribution of a flux-line, and flux-line dynamics activated by heat and current, have employed the high spatial resolution and magnetic sensitivity of electron holography. And recently, the 2-D static distribution of vortices was also observed by this technique. However, real-time observations of the vortex lattice, in spite of scientific and technological interest, have not been possible due to experimental difficulties. Here, we report the real-time observation of vortex lattices in a thin superconductor, by means of Lorentz microscopy using a 300 kV field emission electron microscope. This technique allows us to observe the dynamic motion of individual vortices and record the events on a VTR system.The experimental arrangement is shown in Fig. 1. A Nb thin film for transmission observation was prepared by chemical etching. The grain size of the film was increased by annealing, and single crystals were observed with a thickness of 50∼90 nm.

scholarly journals Direct Observation of Nanoscale Magnetization Reversal and Spin Dynamics Using In-Situ Lorentz Microscopy and Electron Holography

2010 ◽  
Vol 16 (S2) ◽  
pp. 576-577
Author(s):  
L Huang ◽  
Y Zhu
Keyword(s):  
Direct Observation ◽  
Magnetization Reversal ◽  
Spin Dynamics ◽  
Electron Holography ◽  
Lorentz Microscopy

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Determination of the Inelastic Mean-Free-Path and Mean Inner Potential for AlAs and GaAs Using Off-Axis Electron Holography and Convergent Beam Electron Diffraction

2007 ◽  
Vol 13 (5) ◽  
pp. 329-335 ◽  
Author(s):  
Suk Chung ◽  
David J. Smith ◽  
Martha R. McCartney
Keyword(s):  
Electron Diffraction ◽  
Theoretical Calculations ◽  
Mean Free Path ◽  
High Energy ◽  
Convergent Beam Electron Diffraction ◽  
Electron Holography ◽  
Beam Electron ◽  
The Mean ◽  
Convergent Beam ◽  
Inelastic Mean Free Path

The mean-free-paths for inelastic scattering of high-energy electrons (200 keV) for AlAs and GaAs have been determined based on a comparison of thicknesses as measured by electron holography and convergent-beam electron diffraction. The measured values are 77 ± 4 nm and 67 ± 4 nm for AlAs and GaAs, respectively. Using these values, the mean inner potentials of AlAs and GaAs were then determined, from a total of 15 separate experimental measurements, to be 12.1 ± 0.7 V and 14.0 ± 0.6 V, respectively. These latter measurements show good agreement with recent theoretical calculations within experimental error.

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