Observation Of Magnetic Domain Structures Research Articles

Theoretical and experimental studies of magnetic domains

The primary purpose of this paper is to review recent contributions from North American scientists to theory and observations of magnetic domain structures in magnetic minerals common to rocks.Although rock magnetism deals with all the magnetic properties of rocks, a major goal of rock magnetists has been to understand the origins and properties of remanent magnetization (RM). A remanent magnetization is defined as the magnetization that exists in the absence of an external magnetic field. The analyses of RMs (of which there are more than 20 kinds) have led to the numerous, and well‐known, successes of paleomagnetism.

Moving characteristics of magnetic domains in FeCrAl damping alloys

The dynamic observation of magnetic domain structure and motion of domain walls within ferrite in FeCrAl series ferromagnetic damping alloys were investigated using an in-situ technique in an electron microscope equipped with a tensile stage. Results showed that the motion of magnetic domain under external stress was accomplished through the disappearance of part prior domain walls, the formation of new walls and the reconfiguration of prior and new domain walls. The characteristics of magnetic domain motion within ferrite were preliminarily researched.

Conversion electron Mössbauer spectroscopy of the surface crystallization of the Fe75Co9B16 amorphous alloy

Using a new design of helium-methane gas-flow detector of conversion electrons for Mossbauer spectroscopy, non-uniform nucleation of the primary α-Fe-Co phase on both contact and free surfaces of the Ar(+H2) annealed amorphous Fe75Co9B16 alloy was observed in its early crystallization stage. In this state the amount of crystalline phase on the contact ribbon side surpasses that on the free one by a factor of three, whereas no traces of volume crystallization were observed in the transmission spectra. By applying ion implantation to both ribbon surfaces, a slight reduction of the crystalline phase contribution was found. Magnetic domain structure observations were performed in order to evaluate the influence of surface crystallization on magnetic properties.

Demagnetization and magnetic domain structure of silicon steel sheet

In this paper the condition of the optimum demagnetization is discussed by using the observation of magnetic domain structure. The pattern of magnetic domain structure is indicated under various demagnetizing conditions: amplitude, frequency and time. The number of domains increases with increasing frequency and gradient of the demagnetizing magnetic flux density. The optimum demagnetizing conditions are above the residual flux density, frequency 100–200 Hz, and small gradient.

X-Ray Topographic Observations of Magnetic Domain Structures and 180° Walls in a (100) Crystal of Pure Iron under an External Magnetic Field

Magnetic domain structure in a (100) crystal of pure iron of about 70 µm in thickness was investigated under an external magnetic field by X-ray transmission topography. Several kinds of images in the <100> directions were observed in the crystal under the magnetic field of about 20 Os. They are simple 180° wall images, wall images having a periodic intensity of contrast and wall images having <100> images. In particular, the 180° wall images having periodic contrast are observed in the crystal only under the magnetic field, and vanish after removal of the magnetic field. Furthermore, the magnetic domain structure under the magnetic field was discussed.

Magnetization reversal in ultrathin ferromagnetic films with perpendicular anistropy: Domain observations

We report on the first observation of magnetic-domain structure during spin reversal under field in ultrathin metallic films with perpendicular anisotropy. The magnetization reversal is either dominated by the nucleation process or by domain-wall motion. The related magnetic aftereffect is analyzed starting from the Fatuzzo theory.

Interferometric and holographic techniques in transmission electron microscopy for the observation of magnetic domain structures

The present state-of-the-art of electron interferometry and holography applied to the investigation of micromagnetic structures in thin ferromagnetic specimens is given. A short account is reported of the interaction of the electron beam with the specimen, followed by considerations concerning the relation between the detected phase information and the magnetic structures of the specimen. The working principles of the two electron interferometer methods, based on wave-front and amplitude division devices, are reviewed. Finally, the experimental results obtainable by the above mentioned techniques are presented and compared with the observations resulting from the Lorentz microscopy.

Observations of magnetic domain structures in thick foils of Ni-Fe-Co-Ti alloy

The domain structure of thick foils of a 33.8Ni-51.0Fe-14.0Co-1.2Ti (wt%) alloy has been studied by high voltage transmission Lorentz microscopy. Complex domain structures and wall images have been observed. Periodic domain structures have been interpreted as sets of two-dimensional vortex walls.

Observation of magnetic domain structure in thin ferromagnetic films by electron holography

An overview is provided of a new method that has been developed for observing fine details of magnetic domain structures in thin specimens. In this method, in-plane magnetic lines of force inside a specimen are directly observed in the electron interference micrograph. Quantitative measurement is also possible, since two neighboring contour lines contain a constant magnetic flux of h/e. This method is also applicable to observation of microscopic distributions of magnetic fields. Several practical applications are presented using this technique.

Observation of magnetic domain structures in thin foils at low temperatures by transmission electron microscopy

Observation of magnetic domain structures in thin foils at low temperatures by transmission electron microscopy

Image Formation by Magneto-optic Effects

The observation of magnetic domain structures by means of the Faraday and Kerr effect is described in terms of geometrical and physical optics; experimental techniques and theoretical explanations depend on the magnetic and optical properties of the investigated materials. Two methods are presented considering magnetization objects by means of Kirchhoff's diffraction theory. Starting from the calculation of intensities and polarization states of the diffraction by a magnetization grating, experiments are discussed concerning Fraunhofer diffraction and dark-field observation, artefacts in the image of domains, multiple diffraction by thick specimens, object functions available by magnetic structures and the applications for the investigation of magnetization reversal processes and data processing.

Direct observation of magnetic domain structure in plated-wire memory devices

Direct observation of magnetic domain structure in plated-wire memory devices

High-resolution light-optical observation of magnetic domain structures in CrBr 3

For the first time magnetic domains in thick CrBr 3 single crystals were made visible by light-optics. When cooled without an external magnetic field, meander domains are formed. If, however, a weak magnetic field is applied during the cooling below T c, a strip domain pattern aligned in the direction of this field as well as honeycomb domains show up. The measured domain width is in sufficient agreement with the theoretical value.

The observation of magnetic domain structures of the intermetallic compounds SmCo5, LaCo5 and CeCo5

The observation of magnetic domain structures of the intermetallic compounds SmCo5, LaCo5 and CeCo5

Domain Wall Dislocation Interactions in RbFeF3

RbFeF3 is a transparent ferromagnet (below 87°K) with a large Faraday rotation which permits the direct observation of magnetic domain structures in bulk crystals. An etch-pitting solution has been developed which reveals the dislocation configuration existing in the crystals, and it has been demonstrated that RbFeF3 exhibits sufficient plasticity so that arrays of dislocations can be put into crystals. The role of dislocation subboundaries and slip bands as nucleation sites for reversed magnetic domains will be demonstrated. The effectiveness of subboundaries and slip bands as pinning sites for domain walls when subjected to varying dc and ac magnetic fields are discussed.