scholarly journals On the YFe11Mo intermetallic characterization

2013 ◽  
Vol 19 (S4) ◽  
pp. 135-136
Author(s):  
D. Nunes ◽  
A.P. Gonçalves ◽  
J.Th.M. De Hosson ◽  
P.A. Carvalho
Keyword(s):  
Permanent Magnets ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Eutectic Mixture ◽  
Dendritic Morphology ◽  
Type Structure ◽  
Processing Route ◽  
Objective Lens ◽  
X Ray ◽  
Lorentz Microscopy

Rare-earth intermetallic compounds adopting the tetragonal ThMn12–type structure and containing high Fe concentrations have attracted considerable attention in the field of permanent magnets. Among them, the Y-Fe-Mo series has been extensively investigated, especially by X-ray diffraction (XRD), but the microstructural characterization was very limited.In the present work, Y:11Fe:Mo has been prepared by melting Y, Fe and Mo in an arc furnace followed by splat-quenching and/or annealing treatments. The structure, chemistry and magnetic domain configurations of the resulting polycrystalline aggregates have been investigated by XRD, scanning and transmission electron microscopies (SEM and TEM, respectively), energy dispersive X-ray spectroscopy (EDS) and Lorentz microscopy.A special emphasis was given to Lorentz microscopy, where contrast is based on the Lorentz deflection imposed on electrons by the passage through a magnetic specimen. The magnetic domains have been imaged by the intermediate lens in Fresnel mode, with the objective lens switched off. In these conditions the intermediate lens is defocused so that out-of-focus images of the specimen are formed: the magnetic domain walls are imaged as alternate bright (convergent) and dark (divergent) lines. For the overfocused image, bright lines occur at the position of domain walls for which the magnetisation on either side is deflecting the electrons towards the wall, whereas dark lines are observed at the walls for which the magnetisation on either side is deflecting the electrons away from the wall. The opposite contrast is observed at the underfocused image.The results have shown that the tetragonal YFe11-xMoy phase is predominant, with a cellular dendritic morphology (Figure 1), but a considerable presence of -Fe(Mo) could be inferred, forming a coarse intercellular eutectic mixture. Significant Fe segregation occurred during annealing. However, this composition variation corresponded to an extremely limited evolution of the lattice parameters, the Rietveld analysis pointing to Fe vacancies at the 8i sites on the annealed material. XRD and EDS results indicate that the fraction of point defects in the ThMn12-type structure adapts to the processing route and that the stable configuration depends on the temperature. The current study also showed that grain boundaries are usually associated with domain walls and that YFe11Mo grains present internal domain walls forming stripe/maze patterns characteristic of high anisotropy materials (Figure 2), while residual -Fe(Mo) grains exhibit vortex configurations (see arrows in Figures 2 (a-c)).The work was supported by the Portuguese Science Foundation through the CTM/48617/2002 and PEst-OE/CTM-UI0084/2011 grants.

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.

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

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.

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

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.

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.

Synthesis and Characterization of BiFeO3 Ceramic by Simple and Novel Methods

2016 ◽  
Vol 35 (6) ◽  
pp. 551-557 ◽  
Author(s):  
Omid Amiri ◽  
Mohammad Reza Mozdianfar ◽  
Mahmoud Vahid ◽  
Masoud Salavati-Niasari ◽  
Sousan Gholamrezaei
Keyword(s):  
Magnetic Properties ◽  
Domain Walls ◽  
Magnetic Domain ◽  
X Ray Diffraction ◽  
X Ray ◽  
Size Dependent ◽  
Magnetic Domain Walls ◽  
Magnetization Orientation ◽  
Thermal Stability Of

AbstractBiFeO3 nanopowders with new morphology have been synthesized by different methods. X-ray diffraction analysis, scanning electron microscopy, Fourier transform infrared and vibrating sample magnetometer were carried out at room temperature to study the structural and magnetic properties of as-synthesized products. VSM was utilized to measure the size-dependent magnetic behaviors of the as-prepared nanoparticles. Results show that the method has strong effect on the purity of the products. BFO synthesized by third method was pure. Crystallite size has a great effect on the magnetic properties. According to these results the nanoparticle diameter is smaller than the critical single-domain diameter, avoiding the configuration of magnetic domain walls decreases the magnetization. Even though the diameter of particle becomes even smaller, the thermal stability of the magnetization orientation decreases.

scholarly journals Aberration Corrected Lorentz Microscopy to Investigate Magnetic Domain Walls in Co-Pt Nano-Chessboards

2017 ◽  
Vol 23 (S1) ◽  
pp. 454-455 ◽  
Author(s):  
Isha Kashyap ◽  
Jerrold A. Floro ◽  
Yongmei M. Jin ◽  
Marc De Graef
Keyword(s):  
Domain Walls ◽  
Magnetic Domain ◽  
Lorentz Microscopy ◽  
Magnetic Domain Walls ◽  
Aberration Corrected

Theoretical and Experimental Study of the Diffraction Contrast on Magnetic Domain Walls

1982 ◽  
Vol 37 (5) ◽  
pp. 419-426 ◽  
Author(s):  
M. Polcarová ◽  
J. Brádler
Keyword(s):  
Experimental Study ◽  
Single Crystals ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Dynamical Theory ◽  
X Ray Diffraction ◽  
X Ray ◽  
Magnetic Domain Walls ◽  
Integrated Intensities ◽  
Good Agreement

Dynamical theory of the X-ray diffraction on a crystal containing misfit boundary was applied to the interpretation of the contrast observed in X-ray topographs on 90° magnetic domain walls in single crystals of an Fe-Si alloy. The integrated intensities were computed for several cases corresponding to the actual conditions of experiments. Good agreement of theoretical and experi­mental results was obtained.

Magnetic Domain Wall-Microstructure Interactions In Low-Carbon Steel

1999 ◽  
Vol 5 (S2) ◽  
pp. 18-19
Author(s):  
V. Radmilovic ◽  
Kannan.M. Krishnan
Keyword(s):  
Domain Walls ◽  
Imaging Technique ◽  
Low Carbon Steel ◽  
Magnetic Domain ◽  
Carbon Steels ◽  
Low Carbon ◽  
Magnetic Domain Wall ◽  
Lorentz Microscopy ◽  
Scientific Challenge ◽  
Insight Into

Nondestructive evaluation of steels is both an important engineering need and a scientific challenge. Recent advances include a SQUID imaging technique that is capable of detecting small changes in stray fields at reasonable spatial resolution. The technique is motivated by the fact that the stray fields, determined by the underlying domain configurations in the material, would provide insight into the microstructure including defects, provided the interactions between the microstructure and the domain walls can be well understood.Initial work is being carried out on 1018 low-carbon steels, plastically deformed in a controlled fashion, with the goal of correlating SQUID images with magnetic domain images measured by Lorentz microscopy in a TEM.Experiments were carried out in a CM200 FEG TEM using the OL field in low-mag (LM) mode, based on a procedure described by Verbist et al [1] and Daykin et al [2].

Atomic Structure-Sensitive Magnetic Domain Structures of Thin Films

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.

Sign in / Sign up

Export Citation Format

Share Document