共查询到20条相似文献,搜索用时 31 毫秒
1.
The competition between surface/interface and intrinsic anisotropies yields a number of specific reorientation effects and strongly influences magnetization processes in diluted magnetic semiconductors as (Ga,Mn)As and (In,Mn)As. We develop a phenomenological theory to describe reorientation transitions and the accompanying multidomain states applicable to layers of these magnetic semiconductors. It is shown that the magnetic phase diagrams of such systems include a region of four-phase domain structure with four adjoining areas of two-phase domains as well as several regions with coexisting metastable states. We demonstrate that the parameters of isolated domain walls in (Ga,Mn)As nanolayers are extremely sensitive to applied magnetic field and can vary in a broad range. This can be used in microdevices of magnetic semiconductors with pinned domain walls. For (Ga,Mn)As epilayers with perpendicular anisotropy the geometrical parameters of domains have been calculated. 相似文献
2.
Ravelosona D Mangin S Lemaho Y Katine JA Terris BD Fullerton EE 《Physical review letters》2006,96(18):186604
We report on current-driven magnetization reversal in nanopillars with elements having perpendicular magnetic anisotropy. Whereas only the two uniform magnetization states are available under the action of a magnetic field, we observed current-induced Bloch domain walls in pillars as small as 50 x 100 nm(2). This domain wall state can be further controlled by current to restore the uniform states. The ability to nucleate and manipulate domain walls by a current gives insight into the reversal mechanisms of small nanoelements and provides new prospects for ultrahigh density spintronic devices. 相似文献
3.
A multilayer Pt/Co/Ir/Co/Pt/GaAs heterostructures demonstrates a long term (to several hours) magnetic relaxation between two stable states of the magnetization of the system. The magnetization reversal of the heterostructure layers occurs both due to the formation of nuclei of the reverse magnetization domains and as a result of their further growth by means of motion of domain walls. The competition between two these processes provides a nonexponential character of the magnetic relaxation. At 300 K, the contributions of these processes to the relaxation are commensurable, while, at temperatures lower than 200 K, the contribution of the nucleation is suppressed and the magnetic relaxation occurs as a result of motion of the domain walls. 相似文献
4.
John L. Eves Naoise Grisewood Remo Hügli Hans-Benjamin Braun 《Journal of magnetism and magnetic materials》2010,322(9-12):1381-1384
Magnetic domain wall racetrack memory samples allow for the controlled motion of isolated magnetic domain walls in a quasi one-dimensional geometry. Here we consider the possibility of the dynamical formation of bound states of domain walls that can be prepared via a suitably chosen external field. Upon switching off the external field, these domain walls oscillate around their common center of mass, with a frequency depending on the relative initial handedness of the domain wall. Such breather states may be observed by detecting the resulting magnetization oscillations. 相似文献
5.
We perform ab initio calculations of the electronic structure and conductance of atomic-size Ni nanowires with domain walls only a few atomic lattice constants wide. We show that the hybridization between noncollinear spin states leads to a reduction of the magnetic moments in the domain wall resulting in the enhancement of the domain wall resistance. Experimental studies of the magnetic moment softening may be feasible with modern techniques such as scanning tunneling spectroscopy. 相似文献
6.
M. Ya. Ovchinnikova 《Journal of Experimental and Theoretical Physics》2007,104(3):474-485
The properties of the diagonal stripe structures of the Hubbard model are theoretically studied in relation to the incommensurate spin order and the magnetic effects detected in the dielectric phase of low-doped La2?y SryCuO4 (y ≤ 0.05). The mean-field approximation is used to investigate the properties of the solutions with domain walls between antiphase antiferromagnetic domains that are centered on bonds. Such periodic structures with 2l sites in a unit cell are shown to have 2(l ? 1) levels in the lower and upper Hubbard subbands and two levels that are separated into the Hubbard gap and correspond to quasi-one-dimensional states localized on domain walls. The calculation results are employed to check the assumption that the low conduction of the dielectric LSCO phase occurs via the network of domain walls. The maximum relative change in the magnetoresistance during a spin-flop transition in a critical magnetic field is estimated, and the giant magnetoresistance is qualitatively explained. 相似文献
7.
Conditions at which magnetic inhomogeneities like 0° domain walls arise in (111) plates with combined anisotropy and the properties
of these inhomogeneities are studied. In local magnetic fields, the inhomogeneities may behave as stable states. Their role
in magnetization reversal of the crystals is demonstrated. 相似文献
8.
R.L. Stamps 《Surface science》2007,601(24):5721-5725
Recent theoretical results are highlighted that illustrate some of the interesting phenomena associated with magnetic domain boundary walls. Two problems will be discussed: dynamics associated with domain wall propagation, and effects related to spin transport through domain walls. For the first problem, an example of wall interaction and motion through a random potential will be discussed with reference to the general problem of roughening transitions. Images of domain dynamics in thin films of ion irradiated Co reveal a de-roughening transition associated with long range magnetostatic interactions between pairs of domain walls. A scaling theory of this transition is described in which a curious type of dynamic hysteresis can occur. For the second problem, results from calculations of ballistic charge and spin transport through domain boundary walls are discussed in terms of an effective circuit model. 相似文献
9.
V. V. Kostyuchenko 《Physics of the Solid State》2002,44(1):98-101
The structure of domain walls in magnetic multilayers is investigated taking into account the uniaxial anisotropy and biquadratic exchange between the layers. Analytical solutions are derived for different types of domain wall structures. The majority of the solutions obtained have no analogs in conventional magnetic materials. The thickness and the energy density per unit area are calculated for the domain walls under investigation. The range of parameters that correspond to more energetically favorable structures of domain walls is established. 相似文献
10.
Cobalt antidot arrays on membranes: Fabrication and investigation with transmission X-ray microscopy
L.J. Heyderman S. Czekaj F. Nolting D.-H. Kim P. Fischer 《Journal of magnetism and magnetic materials》2007
We have developed a method to fabricate ferromagnetic antidot arrays on silicon nitride membrane substrates for electron or soft X-ray microscopy with antidot periods ranging from 2 μm down to 200 nm. Observations of cobalt antidot arrays with magnetic soft X-ray microscopy show that for large periods, flux closure states occur between the antidots in the as-grown state and on application of a magnetic field, domain chains are created which show a spin configuration at the chain ends comprising four 90° walls. Pinning of the domain chain ends plays an important role in the magnetization reversal, determining the length of the chains and resulting in preservation of the domain chain configuration on reducing of the applied magnetic field to zero. 相似文献
11.
12.
Z. Wang F. Z. Huang X. M. Lu J. S. Zhu 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,75(2):217-221
The profiles of antiferromagnetic domain walls in
hexagonal manganites RMnO3 are obtained numerically depending on
anisotropy and internal strain due to the lattice distortion at the
ferroelectric domain walls. It is found that the piezomagnetism can lower
the free energy of the system thus it favors the coupling between electric
and magnetic domain walls. Due to the piezomagnetic effect, the clamped
antiferromagnetic domain walls with spin orientation angle ψ changing
from 0 to π have different profiles comparing with those of ψ
changing from 0 to -π, and the former is energetically more favorable
than the latter when the internal strain is tensile at the FEL domain walls
while it is the contrary for compressive strain. Moreover, the strongest
coupling between the FEL domain walls and the favorable AFM domain walls can
be achieved at an optimized internal strain. 相似文献
13.
The anomalous Hall effect has been used as a versatile tool for the measurement of various transport phenomena in magnetic systems, particularly those with perpendicular magnetic anisotropy. The anomalous Hall voltage responds not only to the magnetization state but also to the position of magnetic domain walls when the magnetic domain passes through the Hall bar structure. In this study, an empirical relation was developed between the Hall voltage and domain wall position in the Hall bar geometry. This relation was first developed by numerical simulations and then, confirmed by analytical formulae. The validity of the empirical relation was finally verified by experimental results. The present empirical relation provides an experimental method for the electric detection of the position of magnetic domain walls. 相似文献
14.
Heise M Hoffmann Ch Abshagen J Pinter A Pfister G Lücke M 《Physical review letters》2008,100(6):064501
We present a new mechanism that allows the stable existence of domain walls between oppositely traveling waves in pattern-forming systems far from onset. It involves a nonlinear mode coupling that results directly from the nonlinearities in the underlying momentum balance. Our work provides the first observation and explanation of such strongly nonlinearly driven domain walls that separate structured states by a phase generating or annihilating defect. Furthermore, the influence of a symmetry breaking externally imposed flow on the wave domains and the domain walls is studied. The results are obtained for vortex waves in the Taylor-Couette system by combining numerical simulations of the full Navier-Stokes equations and experimental measurements. 相似文献
15.
Roya Majidi 《Physica B: Condensed Matter》2012,407(19):4005-4007
In the present work, we have compared the resistance of the 90°, 180°, and 360° domain walls in the presence of external magnetic field. The calculations are based on the Boltzmann transport equation within the relaxation time approximation. One-dimensional Néel-type domain walls between two domains whose magnetization differs by angle of 90°, 180°, and 360° are considered. The results indicate that the resistance of the 360° DW is more considerable than that of the 90° and 180° DWs. It is also found that the domain wall resistance can be controlled by applying transverse magnetic field. Increasing the strength of the external magnetic field enhances the domain wall resistance. In providing spintronic devices based on magnetic nanomaterials, considering and controlling the effect of domain wall on resistivity are essential. 相似文献
16.
Yuri S. Kivshar V. V. Konotop Yuri A. Sinitsyn 《Zeitschrift für Physik B Condensed Matter》1986,65(2):209-223
Forced motion of a domain wall in the presence of fluctuations of external magnetic field and those of the parameters of the magnetic medium is studied. Calculations for the models of magnetic systems described by the sine-Gordon and Landau-Lifshitz equations are presented. It is shown that the driven motion of domain walls is characterized by the time-independent velocity distribution function which is used to calculate various statistical characteristics of the domain wall. Analysis of the mean velocity of the steady motion of the domain wall leads to the conclusion that the presence of a fluctuating magnetic field results in an increase of the effective relaxation constant of the magnetic system. In case of the sine-Gordon model the mean radiation power accompanying the forced motion of the domain wall is calculated. Inelastic interactions of two domain walls of opposite polarities are described. 相似文献
17.
《Journal of magnetism and magnetic materials》2001,223(1):63-72
The magnetic domain configurations of exchange-coupled NiO/Co bilayers were investigated by magnetic force microscopy. These bilayers exhibit a well-defined uniaxial anisotropy resulting from the deposition at oblique incidence of the NiO layer. Two types of magnetic contrast are identified: (i) bipolar contrast due to 180° Néel walls in the parts of the walls which are parallel to the easy axis of magnetization, and (ii) monopolar contrast in the parts of the walls separating domains with meeting head-on magnetizations. These latter domain walls have a zigzag shape which represents a compromise between a decrease in the local density of magnetostatic energy and an increase in the wall length. The effect of the Co thickness of the shape on the domains is also discussed. 相似文献
18.
Inhomogeneous states of ferrite-garnet crystals with mixed anisotropy have been studied. A mechanism for the occurrence in these crystals of new types of magnetic inhomogeneities, frozen solitons or 0° domain walls, is presented. Their stability, static properties, and connection with homogeneous metastable states are investigated. The influence of the metastable states on the structure of domain walls of a normal type is also shown.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 51–56, August, 1988. 相似文献
19.
The trajectory of electrons in the stray field of a uniaxial magnetic film containing a strip domain structure (SDS) with a magnetization perpendicular to the sample surface are determined by numerical solution of the equations of motion. The interval of angles between the electron velocity projection onto the film surface and domain walls is determined, in which entry blockage takes place (electron scattering occurs without collisions with the sample surface). It is found that an increase in the electron energy leads to a decrease in this angular interval. The results are analyzed for multiple interactions of an electron moving in the gradient field of an SDS with attracting and repelling domain walls. 相似文献
20.