Magnetic Domains and Domain Wall Pinning in Nanocrystalline Ni-P

Magnetic domain structures in a Ni-5at%P alloy have been examined using Lorentz microscopy in Fresnel mode in a JEOL 2010TEM. with electron diffraction and high resolution electron imaging, the Ni-P alloy material is seen to be of FCC structure and composed of nanometer-sized grains (< 4nm in diameter), which is about 2 orders less in size than that of a single magnetic domain.The TEM specimen was prepared using jet polishing method. Before introducing the specimen into the microscope, the objective lens was turned off in a free lens control mode to ensure that the domain structures in the specimen remain unaffected. The objective mini-lens was used to perform Lorentz imaging with out-focus method.Stripe domains were observed. The width of these stripes is about 0.2 micron. But the length of these domains varies, sometime up to several microns. The stripe domains are grouped, which are near parallel one to the other.

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Magnetic Material Observation Assembly for Tem with a Eucentric Goniometer

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100092669 ◽

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.

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Temperature Dependence of Magnetic Domains and Wall Structures

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010009573x ◽

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.

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Tem Study of Twinning and Magnetic Domains in Terfenol-D

MRS Proceedings ◽

10.1557/proc-360-189 ◽

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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Lorentz Microscopy: Effect of Tilting on Magnetic Domains in Single Crystal Iron Films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100101694 ◽

1968 ◽

Vol 26 ◽

pp. 388-389

Author(s):

L. F. Allard ◽

A. P. Rowe ◽

P. L. Fan

Keyword(s):

Single Crystal ◽

Domain Walls ◽

Magnetic Domain ◽

Objective Lens ◽

Pole Piece ◽

Magnetic Domains ◽

Iron Films ◽

Lorentz Microscopy ◽

Magnetic Domain Walls ◽

Microscopy Techniques

In order to observe magnetic domain walls by Lorentz microscopy techniques it is often necessary either to operate the microscope with the objective lens off, thus severely limiting the magnification, or to move the specimen from its usual position or make some other modification so that the field to which it is subjected is not so strong that it saturates the specimen. However, conditions in the JEM-6A have proved favorable for observation of domains in single crystal iron films by the out-of-focus method without any modifications, using either the regular specimen stage with the small bore pole piece or the tilting stage with the large bore pole piece. The tilting stage is particularly useful for these studies because the domains are very sensitive to small differences in inclination in the field.

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Lorentz microscopy study of magnetic domain walls in Fe-Cr-Co alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100109458 ◽

1978 ◽

Vol 36 (1) ◽

pp. 462-463

Author(s):

Yalcin Belli

Keyword(s):

Domain Walls ◽

Magnetic Domain ◽

Microscopy Study ◽

Ferromagnetic Phase ◽

Stable Phase ◽

Magnetic Domains ◽

Lorentz Microscopy ◽

Magnetic Hardening ◽

Electron Microscopes ◽

Co Alloys

Fe-Cr-Co alloys have great technological potential to replace Alnico alloys as hard magnets. The relationship between the microstructures and the magnetic properties has been recently established for some of these alloys. The magnetic hardening has been attributed to the decomposition of the high temperature stable phase (α) into an elongated Fe-rich ferromagnetic phase (α1) and a weakly magnetic or non-magnetic Cr-rich phase (α2). The relationships between magnetic domains and domain walls and these different phases are yet to be understood. The TEM has been used to ascertain the mechanism of magnetic hardening for the first time in these alloys. The present paper describes the magnetic domain structure and the magnetization reversal processes in some of these multiphase materials. Microstructures to change properties resulting from, (i) isothermal aging, (ii) thermomagnetic treatment (TMT) and (iii) TMT + stepaging have been chosen for this investigation. The Jem-7A and Philips EM-301 transmission electron microscopes operating at 100 kV have been used for the Lorentz microscopy study of the magnetic domains and their interactions with the finely dispersed precipitate phases.

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Atomic Structure-Sensitive Magnetic Domain Structures of Thin Films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117960 ◽

1985 ◽

Vol 43 ◽

pp. 206-209

Author(s):

S. Tsukahara

Keyword(s):

Thin Films ◽

Magnetic Properties ◽

Domain Walls ◽

Magnetic Domain ◽

Quarter Century ◽

Specimen Handling ◽

Lorentz Microscopy ◽

Domain Structures ◽

Structure Sensitive ◽

Direct Interpretation

Transmission electron microscopy, TEM, that can serve for observation of both atomic and magnetic structures is useful to investigate structure sensitive magnetic properties. It is most effective when it is applied to thin films for which direct interpretation of the results is possible without considering additional effects through specimen handling for TEM use and modification of dimension dependent magnetic properties.Transmission Lorentz microscopy, TLM, to observe magnetic domains has been known for a quarter century. Among TLM modes the defocused mode has been most popular due to its simple way of operation. Recent development of TEM made it possible that an average instrument commercially available could be easily operated at any TLM modes to produce high quality images. This paper mainly utilizes the Foucault mode to investigate domain walls and magnetization ripples as the finest details of domain structure.

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Energy filtered magnetic domain imaging at 400 kV

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100137902 ◽

1995 ◽

Vol 53 ◽

pp. 306-307

Author(s):

N.T. Nuhfer ◽

J. Dooley ◽

M. De Graef

Keyword(s):

Magnetic Domain ◽

Microstructural Characterization ◽

Objective Lens ◽

Magnetic Recording Media ◽

Magnetic Actuator ◽

Lorentz Microscopy ◽

Low Field ◽

Field Environment ◽

Field Area

Lorentz microscopy provides an important technique for the study of advanced magnetic recording media. Recording densities as high as 10 Gbit/in may be within reach in the future. Microstructural characterization of both the crystallographic and magnetic structure of these thin films is needed at the highest spatial resolution. Another area where Lorentz microscopy has proven to be an extremely valuable tool is in magnetic actuator applications, in particular for magnetostrictive alloys, such as Terfenol-D. The standard Lorentz techniques (Fresnel and Foucault imaging) require a low-field environment, so that the sample is not completely saturated during observations. Depending on the microscope type this low-field area can be obtained by either switching off the objective lens and using the weak post-field to focus the image, or by using special low-field pole pieces. The attainable magnification in both cases is usually lower than for conventional TEM. Recently a new low-field lens for the JEOL 4000EX TEM was reported (AMG40, 1 Gauss field strength) with a useful magnification range upto × 200,000. In this paper we report an alternative method to obtain high magnification magnetic domain images at 400 kV.

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Quantification of micromagnetic structure from Lorentz micrographs

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100172206 ◽

1994 ◽

Vol 52 ◽

pp. 894-895

Author(s):

J. Zweck ◽

M. Herrmann ◽

H. Hoffmann

Keyword(s):

Phase Shift ◽

Quantitative Evaluation ◽

Magnetic Induction ◽

Phase Contrast ◽

Magnetic Domain ◽

Contrast Transfer Function ◽

Lorentz Microscopy ◽

Domain Structures ◽

Spatial Frequencies ◽

Microscopy Images

Defocused imaging of magnetic domain structures is a well-known technique to observe the micromagnetic structures in ferromagnetic thin films. Nevertheless, Lorentz microscopy images are rarely subject to a quantitative evaluation of micromagnetic parameters. In this paper, we offer a new method for quantitative evaluation of ripple wavelengths and ripple angle from Lorentz microscopy images carried out on soft magnetic Ni81Fe19 films. The work was carried out using a Philips CM30 electron microscope with a combined Twin/Lorentz lens.The experiments were performed on thin ferromagnetic films of a Ni81Fe19 alloy. Due to the internal magnetic induction within the specimens, the partial electron waves experience a phase shift proportional to the local in-plane magnetic induction , the specimen's thickness t and the lateral distance x from an arbitrarily chosen point of zero phase shift on the specimen. This phase shift can then be imaged using phase contrast methods similar to HREM. Since the phase shifts and the corresponding deflection angles can be very small, a large defocus is necessary to obtain contrast. This large defocus gives rise to an oscillating phase contrast transfer function for the spatial frequencies under observation as well as to a damping envelope for higher spatial frequencies.

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