Observation Of Domain Structure Research Articles

SHG CHARACTERISTIC OF Co-DOPED LiNbO3 SINGLE CRYSTAL

In order to investigate the doping effect of LiNbO 3 by cobalt ion, LiNbO 3 single crystals doped with CoO, 0.02, 0.05, 0.2, and 1 mol% were synthesized. SHG characteristics were measured using CW YAG:Nd laser in the temperature range from 120 to 310 K. Optical absorption measurements were carried out in the wavelength between 300 and 1800 nm in the y direction. The largest conversion efficiency of SHG was observed in the 0.02 mol% doped crystal, which is due to harmonic effect. Microscopic observation of domain structure was also carried out. It is found that the domain layers of positive and negative orientation lie on top of another in the direction of the c axis, the thickness of which is of the order of microns. SHG intensity is discussed based on the relation between laser beam diameter and the thickness of domain layers.

Optical and X-Ray Studies in Ferroelastic Cs3H(SeO4)2

Optical observation of domain structures and X-ray examinations of Cs 3 H(SeO 4 ) 2 were carried out above room temperature. The effect of an external force on the rearrangements of the constituent ions accompanied by the movement of domain boundary was studied at room temperature. The interrelations between unit cells in each phase were obtained above room temperature. When the crystal is warmed up through the phase transition at T II , all the hydrogen bonds are instantaneously broken, and then the hydrogen atoms are so rearranged as to form new hydrogen bonds between two diffrent adjacent SeO 4 -2 tetrahedra. When the domain boundary is moved, the SeO 4 -2 tetrahedra are tilted and displaced to new positions, and simultaneously hydrogen bonds are broken, and then new hydrogen bonds are reconstructed.

Direct Observation of Domain Structures in Triglycine Sulfate by Atomic Force Microscope

Direct observations of domain structures on a cleavage (010) plane of TGS [triglycine sulfate; (NH2CH2COOH)3-H2SO4] are conducted using an atomic force microscope (AFM). The domain structure immediately after a cleavage treatment and its relaxed one are analyzed in detail, especially for the height of domain wall and the transition layer at antiparallel domain walls. Moreover, the positions of glycine and sulfate groups are determined by comparing the observed highly resolved molecular images with the electron-density function obtained from the reported X-ray diffraction data.

Observation of flux lines by electron holography

The wave nature of electrons is utilized through electron holography to directly observe magnetic flux lines, as an electron interference micrograph, with a coherent field-emission electron beam. This technique is applied to the magnetic domain structure observation of a ferromagnetic thin film and also to the direct observation of flux lines penetrating a superconducting thin film. >

Magneto-optical imaging of Shubnikov phase

Among the various methods to obtain images of the Shubnikov phase in superconductors the high-resolution Faraday effect enables one to local (spatial resolution of about 0.8 μm) and dynamic observations of domain structures. In this paper the different types of flux penetration into the different kinds of high-T c samples (sintered materials, single crystals and thin films) are presented. It is found that the obtained domain structures of single crystalline materials depend strongly on the geometry of the samples. The possibility to local observations allows to study the influence of various microstructures on the pinning behaviour. As a new feature of the high-T c superconductors, it is shown that in the remanent state vortices of opposite polarity have nucleated at the sample edges. Domain patterns of high energy heavy-ion irradiated high-T c samples show the advantages of a local determination of the acting volume pinning forces and critical current densities. Using the capability to dynamic observations, flux creep effects can be visualised.

Bitter colloid observations of magnetic structures in perpendicular magnetic recording media

In this study the Bitter colloid method has been used for domain structure observation in high coercivity Co-Cr and for observations of magnetization state of single alumite needles. Furthermore the results of bit writing experiments in Co-Cr have been observed by this method, which allows to compare samples, prepared with different parameters.

Forming of the domain structure in lead germanate during phase transition

Abstract The results of the observation of as-grown domain structure in lead germanate Pb5Ge3O11 (LGO) by specially deviced cleavage method are presented. The influence of periodic composition inhomogeneties (growth layers) is investigated. It is shown that the observed at room temperature frozen-in domain pattern is defined by the orientation of growth layers relative to the polar axis and selfreconstruction of domain distribution during cooling.

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.

First Order Quasi-Phase-Matched Second-Harmonic Generation in LiTaO3 Utilizing a Periodic Domain Inversion Created by an External Stress

AbstractFirst order quasi-phase-matching in a proton exchanged LiTaO3 channel waveguide structure is reported, where the periodic domain inversion is created by the application of a periodic compressive stress near the Curie temperature. The processing conditions, driving force, and effects on resulting domain structure is reported, including the observation of domain structures with periods as small as 0.36 μm. A waveguide second-harmonic generation structure with a periodic 3.45 μm domain inversion structure is fabricated and evaluated to quasi-phase-match 420 nm blue light with 840 nm output available from standard laser diode sources.

Measurement of Dielectric Constant Near 170 K in (CH3NH3)5Bi2Cl11Single Crystal

Measurement of the dielectric constant and optical observation of domain structure in (CH 3 NH 3 ) 5 Bi 2 Cl 11 have been carried out in the temperature range including 170 K, which has been regarded as a transition temperature. No indication of any phase transition was obtained near 170 K. Temperature dependence of the dielectric constant in this temperature range has been explained applying the Landau theory.

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.

Ferroelastic Domain of (CH3NH3)4InCl7 and Its Phase Transitions

Optical observation of domain structure, differential thermal analysis, dielectric and dilatometric measurements of (CH 3 NH 3 ) 4 InCl 7 have been carried out over a temperature range from 25°C to 200°C. It has been found that the crystal undergoes phase transitions at 194°C ( T 1 ) and 190°C ( T 2 ), and is ferroelastic below T 1 . Taking account of the strain-compatibility relations for domain boundaries, it is suggested from the result of optical observation that the crystal symmetry is m m m , 2/ m and 2/ m in order of descending temperature.

Magnetic properties of TmFeO3 and TmGa0.13Fe0.87O3 orthoferrites

The magnetization σc has been observed to depend strongly on temperature and biasing field in the Γ4-phase. Two families of σc (T) occur corresponding to the poly-domain (H < 200 Oe), and mono-domain (H > 200 Oe) states of the samples. This was proved by observation of domain structures in these samples. In addition to the maximum due to the second-order phase transition Γ2-Γ4, we have revealed a maximum in the susceptibility curves Xc(T) at the high-temperature point of phase transition. The second maximum strongly depends on the biasing field value. Domain structure behaviour in that temperature range, and in various external fields, allowed us to suggest that there exists a relation between this maximum and the shifting processes of domain boundaries, which create a significant susceptibility along the c-axis.

Improvement in ductility of Ni 3Al by γ former doping

Ductility of Ni 3Al macroalloyed with a γ former and a γ′ former has been examined on the basis of the assumption that lowering of ordering energy is responsible for ductility improvement of macroalloyed Ni 3Al. It was found that the addition of γ formers such as palladium, platinium copper and cobalt improves the ductility of Ni 3Al, whereas alloys containing γ′ formers such as tantalum, molybdenum, niobium, zirconium, vanadium, titanium and silicon remain brittle. In addition, observations of antiphase domain (APD) structures in melt-spun ribbons of macroalloyed Ni 3Al revealed that the addition of γ formers effective in ductilizing lowers the ordering energy of Ni 3Al, whereas that of γ′ formers ineffective in ductilizing raises the ordering energy of Ni 3Al. It is concluded that the addition of a ternary element lowering the ordering energy of Ni 3Al is strongly associated with the ductilization of Ni 3Al.

Magnetic rotational hysteresis energy in Nd [sbnd]Fe [sbnd]B permanent magnet with different Cr concentration

The rotational hysteresis energy W r and rotational hysteresis integral R were analysed and compared with theoretical models in order to obtain information on magnetization reversal process of4Nd Fe B magnet with different Cr concentration (from 0 to 5.5 wt%). Observation of the magnetic domain structure was made by means of the powder pattern technique.

Phase Transitions in (CH3NH3)4InBr7

Measurements of the dielectric constant, the DTA signal and the linear thermal expansion, optical observation of domain structure and X-ray examination of (CH 3 NH 3 ) 4 InBr 7 have been carried out over a temperature range from 25°C to 180°C. It is found that the crystal undergoes phase transitions at 171°C ( T 1 ) and 141°C ( T 2 ), and is ferroelastic below T 1 . The crystal at room temperature belongs to monoclinic P2/ n with lattice parameters: a =16.854(6) A, b =7.731(6) A, c =16.756(9) A and β=103.22(2)°. When the symmetry is approximated as to be pseudo-orthorhombic by taking a ′ = a + c , b ′ = b and c ′ = c - a (β ′ =90.34(11)°), the domain structure observed below T 1 is deduced from the strain-compatibility relations for the domain boundaries by taking account of the symmetry change from mmm to 2/ m at T 1 . At T 2 no change of domain configuration has been detected.

Direct observation of domain structure in condensed monolayer phases.

Fluorescence microscopy with polarized excitation allows regions of uniform tilt to be seen within domains of the liquid-condensed phase in monolayers of esters at the air/water interface. Transitions between a tilted and an utilted phase have been observed. Tilt regions within domains form regular six-arm patterns that are analogous to the star defect in films of liquid crystals. It is shown that six-arm stars are to be expected in these monolayers. A second transition has also been observed at lower temperatures.

Direct observation of domain structures and interface dislocations in M7C3by high-resolution electron microscopy

The domain and defect structures of M7C3 with a lattice parameter ratio b/a not-equal square-root 3 in a cast-iron based superalloy have been studied by transmission electron microscopy. High-resolution (HR) images viewed along the exact [001] beam direction have displayed domains with threefold rotational symmetry and interface dislocations which lie on the prismatic plane of the hexagonal sublattice. The antiphase boundaries on (110) planes have also been detected in the [111] HR images.