Lancet Domains Research Articles

The calculation of magnetic domain and magnetostriction in stressed grain-oriented silicon steel

A calculation model for magnetic domain configuration and magnetostriction in grain-oriented silicon steel under tension stress is proposed. The surface lancet and transverse domains in demagnetization and magnetization states are calculated as a function of grain orientation and tension stress. Magnetostriction is calculated by incorporating the critical conditions for disappearance and reappearance of the transverse domain during the magnetization process. The magnetic domain and magnetostriction vary obviously with tension stress and misorientation angle, especially in the ranges of 5–20 MPa and 1°–5°. Negative magnetostriction is quantitatively evaluated in terms of the contribution of the reappeared transverse domain. The calculation model can accurately characterize the magnetostriction of grain-oriented silicon steel under tension stress based on the normal distribution of misorientation angle.

The magnetic domain rotation in the magnetostriction process of Fe-Ga alloy

The domain rotation process during magnetostriction in Fe-Ga rolled sheet has been clarified. The magnetic domain pattern variation with magnetic field of rolling surface was observed by magneto-optic Kerr Microscopy in-situ. According to the sample information and magnetostriction, different magnetic domain structures were constructed for different magnetization stage. In the demagnetized state, the magnetic domain structure of Fe-Ga rolled sheet was closure domain with lancet domain as supplementary domain, and when the magnetic field is larger than 8.3 kA/m the magnetic domains is lancet domains, which well explains the domain rotation process at the stage of slow magnetostriction growth. Using an equivalent stress, the magnetostriction of Fe-Ga polycrystal was simulated by an energy-based domain rotation model. The result fits well with the measured magnetostriction in rapid growth stage and saturation stage. These two models work as a complement to each other and clearly show the domain rotation process during magnetostriction.

Temperature Dependence of Lancet Domains in Grain-Oriented Fe-3%Si Steels

Grain-oriented Fe-3%Si steels are industrially important soft magnetic materials that are usually used in transformer cores but have also recently started to be used in motor cores [1]. Further improvements in the magnetic properties of grain-oriented steels are required to increase the efficiency of electrical machinery. The magnetic properties of grain-oriented steels strongly depend on the magnetic domain structures. The magnetic domains in grain-oriented steels mainly consist of the 180° basic domains and supplementary domains, such as lancet domains. The lancet domains, which occur due to a tilt angle of the [001] easy axis out of the steel surface (β), affect not only iron losses but also magnetostrictive noise. Therefore, it is important to understand the behavior of the lancet domains in order to further improve the magnetic properties. Many studies of the lancet domains [2-4] have been performed, for example, under applied stresses and external magnetic fields at the room temperature (RT). However, the behavior of lancet domains in the region above RT has not yet been investigated even though the operating temperature of transformers and electric motors are generally above RT. In this paper, the changes in the lancet domains of grain-oriented steels over the range from RT to the Curie point were observed using photoemission electron microscopy combined with X-ray magnetic circular dichroism (XMCD-PEEM). Moreover, the domain theory enabled us to quantitatively explain the observed temperature dependence of the lancet domains.

Magnetic Domain Motion and Magnetostriction in the Fe–Ga Sheets

The magnetic domain motion with varying magnetic field is investigated by magneto-optic Kerr microscopy on a slightly Goss misoriented Fe–Ga rolled sheet, and a close relationship between the magnetostriction and the domain motion is reported during the magnetization process. Along the rolling direction (RD), a high magnetostriction value $\lambda _{\mathrm { {//}}}$ of 281 ppm is observed under no prestress for the sheet. The magnetic domains on the $\sim 12^{\circ }$ misoriented Fe–Ga (110) surface appear in the lancet shape and align as lancet comb structures. The lancet domain motion on the surface well explains the magnetostrictive performance $\lambda _{\mathrm { {//}}}$ with the consideration of 90° domains within the lancet structure. The rapid increase of magnetostriction is attributed to the quick motion of 90° domains within the lancet structure under the field below $70\sim 100$ Oe. Under the higher magnetic field, these lancet domains gradually disappear with the field increasing, accompanied with the approach to the saturation magnetostriction along the RD.

Calculation of Basic Domain Width Considering Lancet Domains in (110)[001]Fe3%Si

This paper presents the calculation method of basic domain width in demagnetized states of (110)[001]Fe3%Si under tensile stress in the range of lancet domain occurrence. Accurately calculating the 180 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> basic domain width in demagnetized states is one of the important estimations to evaluate the anomalous eddy-current losses. Previously, stripe domain models, under sufficient strong tensile stress to annihilate lancet domains, were used so that the discrepancy between the calculated and the observed widths under tensile stress in which lancet domains occur became large. Applying the decrease of the surface magnetic charge by lancet domains to calculations of the stray field energy of basic domains enables us to accurately evaluate the 180 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> basic domain width under tensile stress in demagnetized states. Furthermore, the eddy-current losses evaluated using the calculated basic domain width show good agreement with the measured values under the tensile stress in the range of lancet domain occurrence.

Effect of ${\rm D}0_{3}$ Ordered Phase on Total Loss of 6.5 wt% Grain-Oriented Silicon Steel

B2 and D03 antiphase domains are known to increase the total loss of high silicon steels due to the hindrance of magnetic domain movement. In order to investigate a detailed effect of the ordered phases on total loss behaviors, 6.5 wt% grain-oriented silicon steels were fabricated by the diffusion of SiO2 textiles and annealed at 600° with different annealing time. With increasing the annealing time, the average sizes of the antiphase domains increased and moreover the boundary character of D03 antiphase changed from 1/4〈111〉 to 1/2〈100〉. These new boundaries were observed to be anisotropically grown and to increase a lancet domain density. And this increase of the lancet domains density led to increase the total loss because these new boundaries introduced additional strain to the matrix. These results suggest that the formation of the D03 -type 1/2〈100〉 antiphase boundaries should be controlled to reduce the total loss of high silicon steels.

Grain Boundary Penetration by Lancet Domains in Fe-3%Si Grain-Oriented Steel

We studied the influence of the grain boundary characteristics on the configuration and behavior of domains in the vicinity of a grain boundary in grain-oriented (GO) electrical steel. We evaluated the boundary misorientation and microstructure with electron backscatter diffraction and transmission electron microscopy. We used magneto-optic Kerr microscopy to investigate the magnetic domain structure and the domain wall motion at the grain boundary at various external field strengths. We found that the grain boundary geometry has a pronounced influence on the ability of domain walls to penetrate the grain boundary during the magnetization process. The results show that different external field strengths are required for the magnetic saturation of the regions within GO steel having grain boundaries with different characteristics. A tilted grain boundary with a boundary plane normal making an angle less than 10° to the rolling direction allowed for the easy penetration of the lancet domains during magnetization, suggesting that this type of grain boundary affects the properties of GO electrical steels less negatively.

一方向性けい素鋼板の磁区模様に与える減磁の影響

This paper describes domain patterns in grain-oriented silicon steel after the application of rectangular wave induction in the easy and hard magnetization directions. More lancet domains appear after application of rectangular wave induction than after demagnetization by ac induction in the easy magnetization direction.In the hard magnetization direction, the 180° wall spacing and lancet domain density do not change after ac and rectangular wave demagnetization. The domain pattern suggests that the increase in the lancet domain and its deviation cause the ac magnetostriction deviation after application of rectangular wave induction.

Strain-magnetization properties and domain structure change of silicon steel sheets due to plastic stress

The effects of tensile stress and strain on magnetization and magnetic domains in silicon steel sheets were investigated. The strain-magnetization properties of plastic deformation regions under stress showed peculiar characteristics. We observed lancet domains in a sample after removing plastic stress, and found that the appearance of lancet domains was the cause of peculiar stress magnetization characteristics.

Strain-Magnetization Properties and Domain Structures of Silicon Steel Sheets with Stress Applied to Plastic Deformation Regions

The effects of tensile stress and strain on magnetization and magnetic domains in grain-oriented silicon steel sheets were investigated. The strain-magnetization properties of plastic deformation regions under stress showed peculiar characteristics. The magnetization increased with decreasing strain and, after reaching a peak value, decreased with decreasing strain. We observed Lancet domains in a sample after removing stress applied to a plastic deformation region. This phenomenon can be explained by changes in the domain structures, which were partly observed. The results obtained in this investigation can be applied to the nondestructive detection of fatigue in metallic magnetic materials.

Domain structures in silicon-iron in the stress transition stage

Static domain structures in grain-oriented 3% silicon-iron strip have been studied using the Kerr magneto-optic technique when the material was subjected to longitudinal stresses in the range from zero to /spl plusmn/30 MPa. Observations were made while the sample was in a mechanical stressing machine. A typical grain containing bar and lancet domains at zero stress was studied. Irreversible domain subdivisions were found after application of a compression of -20 MPa. A stress domain structure was observed all over the grain at a stress of +30 MPa. Observation in the transition region revealed that the spread of the stress pattern under tension started at the more misoriented grains and spread to the less misoriented regions. Quantitative agreement was obtained with some earlier works but grains with mixed stress and normal domain patterns and regions containing curved domains are thought to be reported, for the first time.

Effect of crystal orientation on the iron loss and magnetostriction in domain refined highly grain oriented Si steel sheets

Iron loss and magnetostriction in domain refined highly grain oriented Si steel sheets were investigated. The degree of grain refining effect on iron loss has been found to be significantly influenced by crystal orientation. This phenomenon is explained by that reappearance of lancet domains during magnetization is strongly influenced by the tilt angle of [001] axis from sheet plane.

Magnetization process and magnetostriction of a four percent Si-Fe single crystal close to (110)[001

The magnetization process in a cube-on-edge Si-Fe single crystal whose tilt angle θ of the [001] axis to a specimen surface is small is experimentally clarified and explained from the viewpoint of the magnetic energy. The relation between the magnetostriction and the domain structure varying with induction is made clear. It is shown that the magnetostriction in the specimen used is quantitatively explained from consideration of the variation of volume of the 90° domain within a lancet structure, which expands or contracts accompanied with a displacement of the main 180° walls in the region of 0 \leq B and also with variation of the magnetizing force that directly acts upon the lancet domains in the region of B_{merge} \leq B .

Quantitative untersuchung der supplement-domänenstruktur von kornorientiertem elektroblech A quantitative investigation into the supplementary domain structure of misoriented grains of transformer steel

The lancet domain structure which is found on slightly misoriented grains of silicon iron transformer steel is analyzed experimentally and theoretically. The results indicate that a misorientation of less than about 1° is needed to avoid supplementary lancet structures entirely, even if the planar stress exerted by the insulation layer is taken into account.