Conventional methods of Lorentz microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 756-757
Author(s):  
H.Roy Geiss
Keyword(s):  
Thin Films ◽  
Electron Beam ◽  
Vector Potential ◽  
Magnetic Thin Films ◽  
Incident Electron ◽  
Objective Lens ◽  
Zero Field ◽  
Magnetic Vector Potential ◽  
Lorentz Microscopy ◽  
Incident Electron Beam

Lorentz electron microscopy has been used to study magnetic domain/domain wall structures in thin films since 1959. Initially the contrast was described in terms of the classical Lorentz deflection of the incident electron beam. As a result Lorentz microscopy has become the general designation given to any of the techniques used to study the magnetic structure with electron beams. However, when sufficiently weak interactions are considered, a more rigorous quantum-mechanical description of the electron-specimen is required. It thus becomes necessary to consider the basis of magnetic imaging as following from the interaction between the magnetic vector potential of the specimen and the incident electron beam. This interaction results in a phase change of the propagating electron beam which is proportional to the path integral of the vector potential. Thus Lorentz microscopy, in reality, is simply phase contrast microscopy for a special class of objects.For many of the magnetic thin films investigated the coercivity of the film is so low that it must be in a nearly zero field environment in order to retain the domain structure. In order to achieve this condition experimentally, the objective lens is usually turned off and the diffraction lens is used as the image forming lens.

Influence of Electron-Beam Annealing Duration on MgB2 Film Superconductivity

2013 ◽  
Vol 745-746 ◽  
pp. 255-260
Author(s):  
Xiang Dong Kong ◽  
Qian Dai ◽  
Han Li ◽  
Qing Rong Feng ◽  
Ming Zhang Chu ◽  
...  
Keyword(s):  
Thin Films ◽  
Electron Beam ◽  
High Efficiency ◽  
Beam Current ◽  
Annealing Duration ◽  
Zero Field ◽  
Superconducting Properties ◽  
Dense Structure ◽  
Novel Method ◽  
The Relationship

A novel method to fabricate Magnesium diboride ( MgB2) film by electron beam annealing was presented. The MgB2 thin films could be prepared in a second or sub-second without any toxic diborane gas, extra Mg vapor or argon gas. The method has the advantages of short formation time and high efficiency. Based on this, the relationship between MgB2 conductivity and electron beam annealing duration was investigated experimentally with an accelerating voltage of 40 × 103 V, a beam current of 3×103 A and different annealing durations of 0.1796s, 1860s, 0.2108s, 0.2200s and 0.2332s. The experimental results showed the MgB2 film with 0.2200s has the highest Tconset , the most dense structure and the strongest diamagnetic signal. Its zero-field Jc at 5 K was 5.0 × 106 A/cm2. Also the variation of the film superconducting properties with the annealing duration was found, it will provide an important reference for the preparation of high-quality MgB2 thin films.

The influence of supporting grid bars on the temperatore increase of a thin fiim subjected to electron irradiation

1990 ◽  
Vol 48 (4) ◽  
pp. 814-815
Author(s):  
A.E. Curzon
Keyword(s):  
Electron Beam ◽  
Cross Section ◽  
Circular Cross Section ◽  
Incident Electron ◽  
Inert Gases ◽  
Main Beam ◽  
Sources And Sinks ◽  
Incident Electron Beam ◽  
Transmission Electron ◽  
Limiting Case

The heating effect of an incident electron beam may cause a material to be radiation-sensitive. For example, the adsorption behaviour of inert gases on graphite observed in a transmission electron microscope depends critically on the temperature of the substrate. Early consideration of beam heating dealt with a circular film illuminated at the centre by an electron beam of circular cross-section. In practice, however, the film is often supported across a square aperture and is not centrally illuminated. It has recently been shown that the method of images may be used to solve the problem of the heating of a square film of thermal conductivity k by a beam whose cross-section is entirely within the film. This solution has the advantage that it applies regardless of where the incident electron beam strikes the film. The general solution involves an infinite sum over a two dimensional lattice of heat sources and sinks. Though the sum is readily evaluated by means of a computer, it is helpful to consider a particular limiting case which is readily understood in terms of three images and the main beam. This case is illustrated in Figure 1.

Zero-field relaxation and exchange interactions in magnetic thin films

2000 ◽  
Vol 63 (2) ◽  
Author(s):  
A. F. Khapikov ◽  
S. Wang ◽  
B. Xu ◽  
J. W. Harrell
Keyword(s):  
Thin Films ◽  
Exchange Interactions ◽  
Magnetic Thin Films ◽  
Zero Field

Electron Channeling Pattern: A Tool for Studying YBaCuO-HTSC Thin Films

1990 ◽  
Vol 209 ◽  
Author(s):  
K. H. Young ◽  
J. Z. Sun ◽  
T. W. James ◽  
B. J. L. Nilsson
Keyword(s):  
Thin Films ◽  
Electron Beam ◽  
Epitaxial Films ◽  
Superconducting Thin Films ◽  
High Angle ◽  
Electron Channeling ◽  
Incident Electron Beam ◽  
Htsc Thin Films ◽  
Non Destructive

ABSTRACTHigh Tc superconducting (HTSC) films synthesis for demanding applications requires epitaxial c-axis growth without high angle grain boundaries. Electron channeling pattern (ECP) analysis using a scanning electron microscope is a non-destructive, fast, direct,and economical tool to determine the orientation and crystallinity of epitaxial films. We have successfully employed this technique to examine our in-situ laser ablated YBa2Cu307−δ superconducting thin films grown on LaAI03 (100) substrates. By changing the energy of the incident electron beam, we can also monitor the film quality vs. depth. The surface bending of YBa2Cu3O7−δ thin films due to the cubic-rhombohedral transition of LaAI03 substrates is also visiblewhen sharp ECPs are present. For films with rough surfaces, the ECP contrast is obscured by unwanted contrast arising from surface features. This unwanted contrast can be minimized by defocusing the electron beam.

Micromagnetics of longitudinal recording media

1991 ◽  
Vol 49 ◽  
pp. 754-755
Author(s):  
P.S. Alexopoulos
Keyword(s):  
Thin Films ◽  
Areal Density ◽  
Magnetic Thin Films ◽  
Detailed Knowledge ◽  
Magnetic Storage ◽  
Storage Devices ◽  
Lorentz Microscopy ◽  
Transition Zones ◽  
Wall Structures ◽  
Deposition Parameters

Future needs in high density magnetic storage devices require increases both in linear and track densities. The latest 1 Gigabit per square inch areal density for longitudinal media demonstrated by IBM has reduced the bit size to dimensions comparable to the characteristic micromagnetic length scales of todays media. Improvement or extension of the current recording limits requires detailed knowledge of micromagnetics and their manipulation or tailoring through the microstructure of the utilized magnetic thin films. There is a number of ways that these parameters can be controlled through the microstructure of the thin films including: chemical alloying, use of nucleating underlayers, and deposition parameters. Our investigation of written transitions recorded on a series of cobalt based alloys using Lorentz microscopy showed that the domain wall structures observed in the transition zones are very complex (Figure 1). The transition zones contain not only zig-zags shape 180° walls but also vortex structures and intermediate states between the two.

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