Simulation of Magnetic Induction Mapping in the TEM

1997 ◽  
Vol 3 (S2) ◽  
pp. 1157-1158
Author(s):  
J. Dooley ◽  
M. De Graef
Keyword(s):  
Objective Lens ◽  
Magnetic Storage ◽  
Experimental Conditions ◽  
Storage Devices ◽  
Lorentz Microscopy ◽  
Full Characterization ◽  
Thin Foils ◽  
Free Region ◽  
High Resolution Tem ◽  
Field Free Region

The design of modern magnetic storage devices with their rapidly increasing information density ne-cessitates a full characterization of the underlying microstructure of the device materials. Lorentz microscopy has for several decades been the main vehicle for micro-magnetic observations. The pri-mary limitation of the Lorentz modes is perhaps the attainable magnification. To avoid saturation, the sample must be placed in a low-field or preferably field-free region in the column, and this invariably means that the microscope can only be operated at low magnifications. Both Fresnel and Foucault images are rather sensitive to the exact experimental conditions which renders quantitative observa-tions quite difficult, if not impossible. Inelastic scattering further limits the usefulness of Lorentz observations to very thin foils.We have recently reported1 a novel Lorentz microscopy setup, combining a Gatan Imaging Filter (GIF) and a JEOL 4000EX top-entry high resolution TEM, operated at 400 kV with the main objective lens switched off.

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.

Design of a high-performance auger spectrometer in the STEM

1988 ◽  
Vol 46 ◽  
pp. 668-669
Author(s):  
Feng Ouyang
Keyword(s):  
High Performance ◽  
Collection Efficiency ◽  
Focal Length ◽  
Spot Size ◽  
Objective Lens ◽  
Energy Analyzer ◽  
Auger Analysis ◽  
Resolution Electron ◽  
Free Region ◽  
Field Free Region

In high resolution electron beam instruments, Auger analysis is usually performed by keeping the sample in a field free region and employing a standard energy analyzer such as hemispherical sector (HSA) or a cylindrical mirror (CMA). In spite of its simplicity, this arrangement results in long focal length operation and consequently a relatively large spot size. In addition, the collection efficiencies of the energy analyzer coupled with such STEM/SEM/SAM systems tend to be small. If however we perform Auger analysis with the sample immersed in the objective lens field, not only would we have the capability of producing a subnanometer diameter probe, but we can also use the post- or pre-specimen field to parallelize the emitted electrons to yield higher collection efficiency.One approach is to use an electrostatic optics extraction system. In this paper magnetic optics extraction will be considered.

Magnetic Material Observation Assembly for Tem with a Eucentric Goniometer

1976 ◽  
Vol 34 ◽  
pp. 540-541
Author(s):  
K. Shi rota ◽  
A. Yonezawa ◽  
K. Shibatomi ◽  
T. Yanaka
Keyword(s):  
Magnetic Material ◽  
Electron Microscope ◽  
Magnetic Domain ◽  
Objective Lens ◽  
Magnetic Domains ◽  
Lorentz Microscopy ◽  
Transmission Electron ◽  
Correction Of Astigmatism ◽  
Single Orientation ◽  
Conventional Transmission Electron Microscope

As is well known, it is not so easy to operate a conventional transmission electron microscope for observation of magnetic materials. The reason is that the instrument requires re-alignment of the axis and re-correction of astigmatism after each specimen shift, as the lens field is greatly disturbed by the specimen. With a conventional electron microscope, furthermore, it is impossible to observe magnetic domains, because the specimen is magnetized to single orientation by the lens field. The above mentioned facts are due to the specimen usually being in the lens field. Thus, special techniques or systems are usually required for magnetic material observation (especially magnetic domain observation), for example, the technique to switch off the objective lens current and Lorentz microscopy. But these cannot give high image quality and wide magnification range, and furthermore Lorentz microscopy is very complicated.

Temperature Dependence of Magnetic Domains and Wall Structures

1972 ◽  
Vol 30 ◽  
pp. 496-497
Author(s):  
Sonoko Tsukahara ◽  
Tadami Taoka ◽  
Hisao Nishizawa
Keyword(s):  
Temperature Dependence ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Iron Film ◽  
Objective Lens ◽  
Lorentz Microscopy ◽  
Domain Structures ◽  
Wall Structures ◽  
Crystal Films ◽  
Metallurgical Structure

The high voltage Lorentz microscopy was successfully used to observe changes with temperature; of domain structures and metallurgical structures in an iron film set on the hot stage combined with a goniometer. The microscope used was the JEM-1000 EM which was operated with the objective lens current cut off to eliminate the magnetic field in the specimen position. Single crystal films with an (001) plane were prepared by the epitaxial growth of evaporated iron on a cleaved (001) plane of a rocksalt substrate. They had a uniform thickness from 1000 to 7000 Å.The figure shows the temperature dependence of magnetic domain structure with its corresponding deflection pattern and metallurgical structure observed in a 4500 Å iron film. In general, with increase of temperature, the straight domain walls decrease in their width (at 400°C), curve in an iregular shape (600°C) and then vanish (790°C). The ripple structures with cross-tie walls are observed below the Curie temperature.

Wear Modeling of Nanometer Thick Protective Coatings

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Jungkyu Lee ◽  
Youfeng Zhang ◽  
Robert M. Crone ◽  
Narayanan Ramakrishnan ◽  
Andreas A. Polycarpou
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Protective Coatings ◽  
Element Model ◽  
Disk Surface ◽  
Magnetic Storage ◽  
Theoretical Frameworks ◽  
Storage Devices ◽  
Parametric Studies ◽  
Magnetic Storage Devices

Use of nanometer thin films has received significant attention in recent years because of their advantages in controlling friction and wear. There have been significant advances in applications such as magnetic storage devices, and there is a need to explore new materials and develop experimental and theoretical frameworks to better understand nanometer thick coating systems, especially wear characteristics. In this work, a finite element model is developed to simulate the sliding wear between the protruded pole tip in a recording head (modeled as submicrometer radius cylinder) and a rigid asperity on the disk surface. Wear is defined as plastically deformed asperity and material yielding. Parametric studies reveal the effect of the cylindrical asperity geometry, material properties, and contact severity on wear. An Archard-type wear model is proposed, where the wear coefficients are directly obtained through curve fitting of the finite element model, without the use of an empirical coefficient. Limitations of such a model are also discussed.

Nanotribological properties of ultra-thin carbon coatings for magnetic storage devices

2003 ◽  
Vol 174-175 ◽  
pp. 1126-1130 ◽  
Author(s):  
B. Jacoby ◽  
A. Wienss ◽  
R. Ohr ◽  
M. von Gradowski ◽  
H. Hilgers
Keyword(s):  
Magnetic Storage ◽  
Carbon Coatings ◽  
Storage Devices ◽  
Thin Carbon ◽  
Magnetic Storage Devices

scholarly journals Magnetic anisotropy of graphene quantum dots decorated with a ruthenium adatom

2013 ◽  
Vol 4 ◽  
pp. 441-445 ◽  
Author(s):  
Igor Beljakov ◽  
Velimir Meded ◽  
Franz Symalla ◽  
Karin Fink ◽  
Sam Shallcross ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
Density Functional ◽  
Magnetic Transition ◽  
Graphene Quantum Dots ◽  
Magnetic Storage ◽  
Magnetic Anisotropy Energy ◽  
Magnetization Direction ◽  
Storage Devices ◽  
Out Of Plane ◽  
Graphene Edge

The creation of magnetic storage devices by decoration of a graphene sheet by magnetic transition-metal adatoms, utilizing the high in-plane versus out-of-plane magnetic anisotropy energy (MAE), has recently been proposed. This concept is extended in our density-functional-based modeling study by incorporating the influence of the graphene edge on the MAE. We consider triangular graphene flakes with both armchair and zigzag edges in which a single ruthenium adatom is placed at symmetrically inequivalent positions. Depending on the edge-type, the graphene edge was found to influence the MAE in opposite ways: for the armchair flake the MAE increases close to the edge, while the opposite is true for the zigzag edge. Additionally, in-plane pinning of the magnetization direction perpendicular to the edge itself is observed for the first time.

Tem Study of Twinning and Magnetic Domains in Terfenol-D

1994 ◽  
Vol 360 ◽  
Author(s):  
Jennifer Dooley ◽  
M. De Graef
Keyword(s):  
Magnetic Domain ◽  
Objective Lens ◽  
Magnetic Domains ◽  
Domain Structures ◽  
Low Field ◽  
Enhanced Resolution ◽  
Transmission Electron ◽  
High Resolution Tem ◽  
Observational Mode ◽  
Lorentz Transmission Electron Microscopy

AbstractThis paper reports the results of detailed TEM observations on [211] oriented single crystal samples of Terfenol-D. Domain structures are interpreted in terms of recent micromagnetic models developed by James and Kinderlehrer. Lorentz transmission electron microscopy was performed on a JOEL 120CX equipped with a low field objective lens. We also report for the first time energy-filtered magnetic domain images, recorded using a Gatan Imaging Filter on a JOEL 40000EX high resolution TEM. This observational mode allows for enhanced resolution and improved image contrast.

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