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1.
The problem of steady motion of the magnetic vortex in a moving domain wall under the action of the Magnus force in weak ferromagnets
was studied. Dynamic bending of the domain wall containing a moving vortex was analyzed. The formulas describing the dependences
of the vortex velocity on the velocity of the domain wall in which it moves were derived. 相似文献
2.
The moving antiferromagnetic vortices are accompanied by solitary deflection waves. These waves allow to investigate generation and nonlinear dynamics of the antiferromagnetic vortices on the moving domain wall with the help of the two- and three-fold digital high speed photography. On the quasi-relativistic domain wall the vortex dynamics is quasi-relativistic with the limiting velocity c=20 km/s, which is equal to the spin-wave velocity. The solitary deflection waves dynamics can be explained assuming existence of the gyroscopic force. A theory for the gyroscopic force in the orthoferrite domain wall is elaborating by A.K. Zvezdin et al. currently. We present a comparison of the theoretical and experimental results on the dynamics of the solitary deflection waves, which accompany the antiferromagnetic vortices in the domain wall of orthoferrites. 相似文献
3.
The stable generation of pairs of antiferromagnetic vortices at a domain wall moving at a velocity of 12 km/s is investigated at the instant it passes through a defect in a thin plate of yttrium orthoferrite. The velocities of a vortex and an antivortex moving in opposite directions along the domain wall and being accompanied by solitary flexural waves are ±16 km/s. The total velocity of antiferromagnetic vortices is close to the maximum velocity of the domain wall, 20 km/s. Such a high velocity can only be due to the action of a quite large gyroscopic force. An external dc magnetic field (±400 Oe) applied along the b axis of the orthoferrite affects this velocity insignificantly. The effective magnetic field that violates the Lorentz invariance of the dynamics considerably exceeds this value. 相似文献
4.
Reflection of solitary flexural waves propagating in a supersonic domain wall of yttrium orthoferrite from the domain wall part moving with the transverse-sound velocity is observed experimentally. This observation confirms that such a reflection of a solitary flexural wave leads to a change in the sign of the topological charge of the antiferromagnetic vortex accompanied by this wave, which proves a direct relationship between these two objects. 相似文献
5.
We deal with the influence of the applied stress on the domain wall velocity in glass-coated magnetic microwires. In general, the domain wall velocity decreases with the applied tensile stress. Four regimes of the domain wall dynamics appear: (1)?diffusion-damped, (2)?a regime with variable domain wall width, (3)?a viscous and (4)?a vortex regime. Detailed analysis of domain wall parameters shows that the structural relaxation plays an important role even at ambient temperatures if high tensile stress is present. At higher fields (viscous regime), the most important damping arises from magnetic relaxation of magnetic moments. Finally, the domain wall velocity steeply increases (reaching a maximum at 7000?m?s(-1)) in the vortex regime and so does the domain wall mobility. 相似文献
6.
M.V. Chetkin Yu.N. Kurbatova T.B. Shapaeva 《Journal of magnetism and magnetic materials》2009,321(7):800-802
The method of generation of antiferromagnetic vortices on the supersound domain wall in the orthoferrites was proposed. Moving antiferromagnetic vortices were accompanied by the solitary deflection waves. These waves were used for investigation of generation and nonlinear dynamics of the antiferromagnetic vortices on a moving domain wall with the help of two- and three-fold digital high-speed photography and Faraday rotation in the orthoferrites plates cut perpendicular to the optical axis. The full velocity of antiferromagnetic vortex nonlinearly increases and saturates on the spin velocity level c. The vortices with smallest topological charges saturate earlier than with big one. The vortices velocity along the domain wall u increases up to the maximum and goes to the dependence u2+v2=c2. Vortex dynamics is quasirelativistic on quasirelativistic domain wall. The theory of gyroscopic force in the domain wall of orthoferrites was elaborated by Zvezdin et al. and was confirmed our earlier experimental results. 相似文献
7.
We investigated the motion of domain walls in ferromagnetic cylindrical nanowires by solving the Landau–Lifshitz–Gilbert equation numerically for a classical spin model in which energy contributions from exchange, crystalline anisotropy, dipole–dipole interactions, and a driving magnetic field are considered. Depending on the diameter, either transverse domain walls or vortex walls are found. A transverse domain wall is observed for diameters smaller than the exchange length of the given system. In this case, the system effectively behaves one dimensionally and the domain wall velocity agrees with the result of Slonczewski for one-dimensional walls. For larger diameters, a crossover to a vortex wall sets in which enhances the domain wall velocity drastically. For a vortex wall the domain wall velocity is described by the Walker formula. 相似文献
8.
In this paper we investigate the role of magneto-crystalline anisotropy on the domain wall (DW) properties of tubular magnetic nanostructures. Based on a theoretical model and micromagnetic simulations, we show that either cubic or uniaxial magneto-crystalline anisotropies have some influence on the domain wall properties (wall size, propagation velocity and energy barrier) and then on the overall magnetization reversal mechanism. Besides the characterization of the transverse and vortex domain wall sizes for different anisotropies, we predict an anisotropy dependent transition between the occurrence of transverse and vortex domain walls in tubular nanowires. We also discuss the dynamics of the vortex DW propagation gradually increasing the uniaxial anisotropy constant and we found that the average velocity is considerably reduced. Our results show that different anisotropies can be considered in real samples in order to manipulate the domain wall behavior and the magnetization reversal process. 相似文献
9.
We have studied the effect of thermal treatment on the domain wall dynamics of FeSiB and FeCoMoB microwires. It was shown that annealing in transversal magnetic field increases the domain wall mobility as well as the domain wall velocity. Annealing under the tensile stress hinders the appearance of the monodomain structure but application of tensile stress leads to the magnetic bistability having the domain wall mobility twice higher that in as-cast state. Further increase of the tensile stress reduces the domain wall mobility but the domain wall velocity increases as a result of the decrease of critical propagation field. Annealing of the FeCoMoB microwire by Joule heating leads to introduction of the circular anisotropy that favors the vortex domain wall. Such treatment increases the domain wall mobility as well as the maximum domain wall velocity. 相似文献
10.
Domain wall dynamics near the limit velocity in a cubic ferromagnet with induced magnetic anisotropy
A research has been conducted into the dynamics of the 180° domain wall in a cubic ferromagnet with induced magnetic anisotropy, this domain wall moving at a velocity close to the limit one. The Landau–Lifshits equation has been reduced to a modified double Sine–Gordon equation with the highest dispersion. A solution has been found which corresponds to the moving 180° domain wall. This paper has determined the dependencies of the velocity of the domain wall's stationary movement on the quality factor and on the ratio of the induced and the cubic magnetic anisotropy constants in slabs with the developed (0 0 1) and (0 1 1) surfaces. 相似文献
11.
Ü . Parts V. M. H. Ruutu J. H. Koivuniemi M. Krusius E. V. Thuneberg G. E. Volovik 《Physica B: Condensed Matter》1995,210(3-4):311-333
When a cylindrical container filled with superfluid 3He---A is rotated around its symmetry axis, several different configurations of quantized vorticity are possible: which of them will be preferred depends on the specifics how the rotating state is formed. The most unusual is the vortex sheet, a domain wall in the order parameter texture into which vortex lines are confined. This metastable structure has the lowest critical velocity of formation if a domain wall with the appropriate orientation is already present in the container. In this case the vortex sheet becomes the preferred rotating state which provides the solid-body rotation of the superfluid component on an averaged scale. Its presence can be identified from the cw NMR spectrum which samples the order parameter texture. Here the experimental properties of the vortex sheet are reviewed, as deduced from NMR measurements. 相似文献
12.
A three-dimensional computer simulation of static magnetization configurations and dynamic processes occurring in a domain wall moving in a uniaxial magnetic film with perpendicular anisotropy has been performed based on the numerical solution of Landau–Lifshitz–Gilbert equations. The calculated static states correspond to a domain wall containing Bloch lines with a surface magnetization distribution that depends on the thickness of the film. It has been shown that these structures can be characterized by particular values of the homotopy index. It has been found that the vortex and antivortex structures existing in the bulk of the film form vortex filaments. A method has been proposed for visualization of the joint motion of vortex filaments and Bloch points, which is based on the numerical calculation of the homotopy index and the winding number. 相似文献
13.
Microprobing of the Dynamic Properties of Transparent Weak Ferromagnets Based on the Domain Boundary
Quantitative dependences of the velocity of a moving domain boundary and sizes of magnetic inhomogeneities in rare-earth orthoferrites are determined experimentally in real time. The results obtained agree satisfactorily with the parameters calculated for the physical model of parametric resonant deceleration of the domain boundary on wall (Winter) magnons. The lower threshold frequency of bending vibrations of the domain wall is of the order of 108 Hz. 相似文献
14.
The dynamics of planar relativistic domain walls is investigated with the help of a new method proposed by Arodz and Larsen. Two solutions are found: one is a steady state domain wall, the other is a nonstationary domain wall. They move with the same constant velocity in the laboratory frame coordinates. When the velocity approaches light velocity c, the "width" of the nonstationary wall inflates very slowly. These domain walls can disappear again soon after their creation in the early universe by moving away from our visible universe. So they would not dominate the universe completely, but keep the observed universe approximately isotropic and homogeneous. 相似文献
15.
J. Olivera R. Varga P. Vojtanik V.M. Prida M.L. Sanchez B. Hernando A. Zhukov 《Journal of magnetism and magnetic materials》2008
Here we report on the domain wall dynamics in amorphous glass-coated FeCuNbSiB microwires measured in the temperature range from 77 up to 400 K. At low temperatures below 200 K, the domain wall velocity is proportional to the applied magnetic field. At temperatures above 200 K, two regions have been found: one with low domain wall mobility at low fields and another one with high domain wall mobility at high fields. The different regions of the domain wall dynamics are treated in terms of the change of the domain wall configuration from transversal to vortex one. Moreover, non-linear regime is shown at low fields at the temperature 373 K as a result of the domain wall interaction with the local defects. 相似文献
16.
Small helical anisotropy was induced in amorphous ferromagnetic Co68.2Fe4.3Si12.5B15 wire by current annealing and simultaneous application of tensile stress and torsion. Presence of helical anisotropy was confirmed by measurement and analysis of the circular magnetic flux versus axial magnetic field hysteresis loops. These measurements also showed that a single domain wall between circular domains can be created by placing the wire in a sufficiently high inhomogeneous magnetic field generated by Helmholtz coils with opposite currents. The domain wall velocity versus axial driving field was measured. The results show that the basic dynamic properties (magnitude of the wall mobility, field interval in which linear dependencies between velocity and field are observed, accelerated increase of the velocity for higher fields) are very similar to those obtained for the domain wall between circular domains driven by a constant circular field. The Hall effect was detected in the eddy current loop generated by the moving domain wall. 相似文献
17.
自耦合射流冲击冷却的数值计算 总被引:2,自引:0,他引:2
本文利用动网格技术对两维自耦合射流冲击冷却恒热流壁面进行了数值模拟,腔体底面具有一定的运动规律,每个时间步网格会重新划分。通过对流场和温度场的分析,得出以下结论:自耦合射流是零质量射流,射流的截面速度分布具有自相似性。涡对的平移和破碎影响了温度场的分布,从而冲击靶面温度最低点不是出现在射流驻点区,而是对应于涡对破碎、紊流度最大的位置。 相似文献
18.
M. V. Chetkin Yu. N. Kurbatova T. B. Shapaeva O. A. Borshchegovskiĭ 《Journal of Experimental and Theoretical Physics》2006,103(1):159-164
An unusual nonlinear relation between the velocity of an antiferromagnetic (AFM) vortex along a domain wall (DW) on the DW velocity is detected. This relation has a maximum whose position depends on the topological charge of the vortex. As the DW velocity increases from the value corresponding to the maximum to its limiting value, the AFM-vortex velocity decreases and tends to zero. The total AFM-vortex velocity increases nonlinearly with the DW velocity and levels off at 20 km/s, which is equal to the velocity of spin waves in the linear section of their dispersion law. The experimental data are approximated satisfactorily. The dynamics of AFM vortices in DWs of yttrium orthoferrite, just as the dynamics of the DWs, is quasi-relativistic and gyroscopic. 相似文献
19.
E. D. Gutlyansky 《Journal of Experimental and Theoretical Physics》2007,105(1):272-277
A method is proposed for describing a moving film vortex structure and its interaction with surface acoustic waves. It is shown that the moving vortex structure can amplify (generate) surface acoustic waves. In contrast to a similar effect in semiconductor films, this effect can appear when the velocity of the vortex structure is much lower than the velocity of the surface acoustic waves. A unidirectional collective mode is shown to exist in the moving vortex structure. This mode gives rise to an acoustic analogue of the diode effect that is resonant in the velocity of the vortex structure. This acoustic effect is manifested as an anomalous attenuation of the surface acoustic waves in the direction of the vortex-structure motion and as the absence of this attenuation for the propagation in the opposite direction. 相似文献
20.
Forgan EM Kealey PG Johnson ST Pautrat A Simon C Lee SL Aegerter CM Cubitt R Farago B Schleger P 《Physical review letters》2000,85(16):3488-3491
We have used the neutron spin-echo technique to measure the small energy change of neutrons which are diffracted by a moving vortex lattice in a low-pinning Nb-Ta superconducting sample. A transport current was passed in the mixed state to cause flux line movement. In the case of uniform motion, the flux velocity v(L) was given as expected by the values of electric and magnetic fields, via E = -v(L)wedgeB. We show that with a nonuniformly moving vortex lattice, one can measure the dispersion of the velocities, opening up new possibilities for investigating moving vortex lines. 相似文献