Papers by Keyword: Domain Wall

Abstract: We present here a method for measuring the temporal Bakehausen scaling exponent in a two-dimensional thin film. The scaling exponent with long-range interaction is observed to be consistent with theoretical and experimental results. In addition, we demonstrate the characteristic exponent with short-range interaction. Our method contributes to the understanding of DW dynamics and helps to optimize spintronic devices.

Abstract: Ferromagnetic film can be a matrix for recording information with the help of magnetic moments of electrons. The study of the processes of changing the magnetic structure in an electron-transmission microscope makes it possible to investigate micro magnetic phenomena. In this paper, we investigate the interaction between the vertices of neighboring regions. It is shown how the magnetic structure of the vertices of the domains changes as they approach each other with the help of an increasing constant magnetic field applied along the axis of easy magnetization. The distance was measured between the vertices of the domains. The schemes of distribution of the magnetization vectors between interacting vertices are shown. These schemes are made from experimental images of the magnetic structure. The distances between domain vertices and domain walls were compared on the basis of experimental data. The film thickness is 50 nm; the structure is Ni_0.83-Fe_0.17. The films were obtained by the method proposed by us. From the experimental results it follows that the interaction of the domain walls is observed at a distance of 20 microns and the interaction of the domain vertices is manifested at a distance of 100 μm.

Abstract: The saturation value of the magnetostriction curve in the [100] direction of a Fe-Ga alloy single crystal was decreased from 226 to 55 ppm by applying the tensile strain of 533 ppm to the measured direction. By magnetic domain observation using a magneto-optic Kerr effect microscope, a complex structure composed of various magnetic domains was observed under zero applied strain. On the other hand, a stripe structure composed of magnetic domains with the magnetization direction in two kinds of <100> magnetic easy directions parallel to the tensile direction, which were separated by straight 180° domain walls, was observed under the tensile strain of 533 ppm. The characteristic magnetic domain structure due to the tensile strain was successfully observed as a cause of the significant decrease of the saturation value of the magnetostriction curve.

Abstract: The present work presents the analysis of Lamb waves in weak easy-axis ferromagnetic yttrium orthoferrite YFeO₃, where the frequency and velocities spectrums were calculated based on dispersion equations. The specialties in calculated Lamb wave spectrum show the possibility of wave generation by an external source. The influence of the sample thickness on the characteristics of wave propagation in a plate is investigated.

Abstract: The work presents the experimental results of the dynamics of the domain wall in the plate of yttrium orthoferrite. In our case the speeds of this motion are much less than the speeds of sound in these crystals. A constant magnetic field was oriented parallel to the plate along the domain wall motion and at the angle ≈ 50° to the sample plane and parallel to the plate along the DW motion. We consider forced vibrations of the domain wall under the influence of weak alternating magnetic fields. The domain walls motion was caused by an alternating magnetic field, which was generated by the coils. The effect of the constant magnetic field on the domain wall dynamics has been found.

Abstract: The domain walls dynamics and generation and evolution of magnetic inhomogeneities of soliton type, emerging in a thin flat layer with the parameters of the magnetic anisotropy, which are different from other two thick layers of the five-layer ferromagnetic structure, were investigated.

Abstract: We have studied effect of current annealing on domain wall dynamics of FeCoMoB microwires. It was showed that 10 minutes of current annealing corresponds to 1 hour of classical annealing in furnace. Moreover, electrical current flowing through microwire produces Oersted magnetic field and therefore circular magnetic anisotropy is induced during annealing. As a result, induced circular magnetic anisotropy prefers vortex domain wall with velocities up to 3 km/s that can be observed in the current annealed nanocrystalline FeCoMoB microwires with much higher temperature stability.

Abstract: Micromagnetic simulation enabled us to fully characterize the nucleation and growth of buried domain walls in a layered hard/soft/hard ferromagnetic thin film. Simulation results show that the exchange spring trilayer exhibits a spiral spin magnetic structure and reveals detailed features of field-dependent domain walls evolution.

Abstract: The magnetization reversal processes of magnetic nanorings (Co₅₀Fe₅₀) with different geometric shapes are investigated. In addition to the expected onion and vortex magnetization states, other metastable states are observed in the magnetization processes. We anatomize the formation and transition of magnetic states, and the propagation and annihilation of domain walls in the reversal process through the dynamic picture. Phase diagrams for the magnetization switching behavior depending on the geometric parameters are presented. The simulation shows that the vortex state is stabilized in thick and narrow rings. The switching field from vortex to onion states turns out to increase with thickness and decrease with width and diameter.

Abstract: We performed magnetic imaging of Ni-based ferromagnetic shape memory alloys. The magnetic microstructure was revealed by Lorentz microscopy and electron holography, which are powerful tools based on transmission electron microscopy. Observations of Ni51Fe22Ga27 and Ni50Mn25Al12.5Ga12.5 alloys, both of which have an L21-ordered structure in the parent phase, demonstrated that the antiphase boundaries (i.e., a type of planer defects) caused significant changes in the magnetization distribution due to depression of the atomic order—actually, the magnetization in these alloys depends upon the degree of chemical order. We propose a method which estimates the important magnetic parameters (the magnetocrystalline anisotropy constant and exchange stiffness constant) based on transmission electron microscopy observations. This method should be useful in magnetic measurements of nanometer-scale areas, for which conventional techniques cannot be applied.