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1.
The finite lifetime T g of a dynamic spiral domain in the anger state in a multidomain film with perpendicular magnetic anisotropy is estimated theoretically in the framework of a dissipative model. The finite lifetime of spiral domains is investigated as a function of the frequency of an external ac magnetic field that varies according to a harmonic law. 相似文献
2.
The stroboscopic method was applied to study the evolution of dynamic spiral domains in garnet ferrite films in an ac magnetic field. The spiral-domain shape was shown to change significantly within a field period; the basic shape transformations take place in the phase range ?π/4 to +π/4 with respect to the polarity inversion time. During the spiral-domain formation or decay, the area and shape of a hysteresis loop of the film region containing the domain gradually change. The upper boundary of the frequency range in which spiral domains form was established to be associated with transformations of the domain wall structure. 相似文献
3.
Yu. I. Dzhezherya A. I. Tovstolytkin 《Journal of Experimental and Theoretical Physics》2008,107(5):794-803
This paper reports on the results of a theoretical investigation into the magnetic and resonance properties of thin films in the range of the transition from a paramagnetic state to a ferromagnetic state in the case where the magnetic transition is a first-order phase transformation. It is demonstrated that, in an external magnetic field directed perpendicular to the film plane, the formation of a specific domain structure consisting of domains of the coexisting paramagnetic and ferromagnetic phases can appear to be energetically favorable. The parameters of the equilibrium system of stripe phase domains and their dependences on the temperature, the magnetic field, and the characteristics of the material are calculated. The specific features of the magnetic resonance spectra under the conditions of formed stripe phase domains are considered. A relationship is derived for the dependence of the resonance field of the system of ferromagnetic domains on the magnetization and temperature. It is shown that the alternating external field can fulfill an orientation function in the formation of stripe phase domains. 相似文献
4.
《Physics letters. A》1997,235(6):643-646
An autowave model of the spiral pattern formation in magnets located in a rotating magnetic field is proposed. The model is based on the overdamped double sine-Gordon equation. Nucleation of spiral domains is associated with the averaged motion of domain walls in the rotating field. A vortex-type defect (Bloch line) is the core of the spiral. 相似文献
5.
Ju. A. Mamalui Ju. A. Siryuk 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(8):1026-1028
Stable spiral domain structures—spiral domains stabilized by a bubble lattice and lattices of spiral domains—in epitaxial ferrite-garnet films have been experimentally investigated. The thermodynamic approach based on the concept of magnetostatic pressure is applied to explain the behavior of a spiral domain structure with a change in temperature or magnetic field. It is shown that phase transitions in spiral domains are related to phase transitions in the bubble lattice. 相似文献
6.
The regions of existence of Anger states in an iron garnet film are plotted and investigated for the first time in a space
of three controlling parameters: the frequency and amplitude of the alternating field and the magnitude of the static bias
field. It is shown that the dynamic spiral domains differ significantly in their configuration and properties in different
regions. A quantitative parameter involving the velocity of the domain walls and the “looseness” (sparseness) of the dynamic
array of magnetic domains is introduce to characterize the favorability of conditions for the formation of spiral domains.
Fiz. Tverd. Tela (St. Petersburg) 40, 1865–1870 (October 1998) 相似文献
7.
Yu. I. Bespyatykh V. Vasilevskii É. G. Lokk V. D. Kharitonov 《Physics of the Solid State》1998,40(6):975-981
Specific models of domain walls are used to investigate conditions for the single-domain state and quasi-single-domain states
in structures with magnetic materials having a quality factor higher than one. It is shown that the critical thickness of
the magnetic film in a tangentially magnetized system decreases monotonically as the magnetizing field increases from zero
to the transition from the collinear to the homogeneous angular phase and then increases monotonically with increasing external
field. In a thin isolated magnetic film, the size of the domains increases exponentially with decreasing thickness. This dependence
is logarithmic near the transition to the single-domain state for a film coated on two sides and obeys a power law for a film
coated on one side. The establishment of a single-domain state and characteristic features in the asymptotic behavior of the
domain structure in magnetic films with and without coatings can be attributed to differences in the asymptotic behavior of
the field of a single domain wall.
Fiz. Tverd. Tela (St. Petersburg) 40, 1068–1074 (June 1998) 相似文献
8.
A. K. Mohapatra S. Chaudhuri S. Roy C. S. Unnikrishnan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):287-298
We report the results from a series of experiments in which
ferromagnetic thin films were used as atom mirrors for laser-cooled
rubidium atoms released from a magneto-optical trap. The thin films were
made of cobalt and lanthanum calcium manganite (LCMO) with thicknesses
between 20 and 300 nm. The magnetic domains in these thin films have
a periodic structure where the spatial period is of the order of the
thickness of the film, and the field decays exponentially above the film
over a length scale comparable to the domain size. Thus, the neutral
atoms reflect off these films from distances comparable to the thickness
of the film, resulting in modification of the reflectivity due to the
competition between the repulsive magnetic force and the attractive
short-range forces such as van der Waals and Casimir forces. The
smoothness of the atom mirror is also modified due to the proximity of
the magnetic domains. The reflectivity is sensitive to the domain
structure and size, which can be modified in LCMO by applying a modest
external magnetic field. In this paper, we discuss the evaluation of the
thin films as magnetic mirrors for atom optics, and the measurement of
the van der Waals force with an accuracy of about 15%, using cobalt
thin films. We also discuss some preliminary results on the
temperature-dependent reflectivity for atoms near the ferromagnetic
transition at 250 K in the LCMO film, and on the domain dynamics and
relaxation. 相似文献
9.
具有条纹磁畴结构的磁性薄膜表现出面内转动磁各向异性,对于解决高频电子器件的方向性问题起着至关重要的作用.本文采用射频磁控溅射的方法,研究了NiFe薄膜的厚度、溅射功率密度、溅射气压等制备工艺参数对条纹磁畴结构、面内静态磁各向异性、面内转动磁各向异性、垂直磁各向异性的影响规律.研究发现,在功率密度15.6 W/cm~2与溅射气压2 mTorr(1 Torr=1.33322×102Pa)下生长的NiFe薄膜,表现出条纹磁畴的临界厚度在250 nm到300 nm之间.厚度为300 nm的薄膜比250 nm薄膜的垂直磁各向异性场增大近一倍,从而磁矩偏离膜面形成条纹磁畴结构,并表现出面内转动磁各向异性.高溅射功率密度可以降低薄膜出现条纹磁畴的临界厚度.在相同功率密度15.6 W/cm~2下生长300 nm的NiFe薄膜,随着溅射气压由2 mTorr增大到9 mTorr,NiFe薄膜的垂直磁各向异性场逐渐由1247.8 Oe(1 Oe=79.5775 A/m)增大到3248.0 Oe,面内转动磁各向异性场由72.5 Oe增大到141.9 Oe,条纹磁畴周期从0.53μm单调减小到0.24μm.NiFe薄膜的断面结构表明柱状晶的形成是表现出条纹磁畴结构的本质原因,高功率密度下低溅射气压有利于柱状晶结构的形成,表现出规整的条纹磁畴结构,高溅射气压会导致柱状晶纤细化,面内转动磁各向异性与面外垂直磁各向异性增强,条纹磁畴结构变得混乱. 相似文献
10.
A. A. Gavrilyuk A. V. Gavrilyuk B. V. Gavrilyuk A. L. Semenov A. V. Semirov N. V. Turik 《Russian Physics Journal》2009,52(1):94-104
Dimensions and energy of domains in the core of an amorphous metal wire are estimated in the work. Influence of the external
magnetic field strength and coercive force on the dimensions of a stable domain is investigated. It is demonstrated that the
highest stability to an external magnetic field and the least energy have domains comprising cylinder and cone-shaped domain
tops and domains with zigzag domain tops.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 83–91, January, 2009. 相似文献
11.
E. G. Lokk M. P. Temiryazeva V. I. Shcheglov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(10):1352-1354
The domain structure (DS) of yttrium-iron garnet films with uniaxial anisotropy fields higher than ∼120 Oe was found to have
a 3D character: there is a stripe domain structure of a certain type in the surface layer and a structure of another type
in the film bulk. It was revealed that in the absence of an external magnetic field, the boundaries of both DSs are almost
perpendicular, whereas with an increase in an external field applied in the film plane along the boundaries of the interior-volume
DS, the boundaries of the surface DS are gradually reoriented along the external field. This phenomenon is theoretically explained
on the basis of the micromagnetic model, which describes DS formation in ferrite films. 相似文献
12.
《Current Applied Physics》2009,9(3):688-690
We recently reported a possible antiferromagnetically coupled phase in a Co-rich CoFeSiB thin film, that had a partially nanocrystalline Co phase in an amorphous CoFeSiB matrix. Although an amorphous CoFeSiB film should show a ferromagnetic behavior, we observed an antiferromagnetic coupling associated with a nanocrystalline Co phase in the hysteresis-loop measurements of Co-rich CoFeSiB thin films. We ascribed the observed antiferromagnetic coupling to dense stripe domains consisting of periodically up and down domains perpendicular to the surface of the film. The configuration of the stripe domains was confirmed with magnetic force microscopy images. When a longitudinal magnetic field was applied, the size of the stripe domain was reduced. While for a transverse field, the domain structure became tilted and zigzagged, but no in-plane magnetic anisotropy was noted. When the magnetic field was increased to values above the saturation magnetic field, HS = 2.5 kOe, the domain structure disappeared. 相似文献
13.
Röhlsberger R Thomas H Schlage K Burkel E Leupold O Rüffer R 《Physical review letters》2002,89(23):237201
We have investigated the magnetic spin structure of a soft-magnetic film that is exchange-coupled to a hard-magnetic layer to form an exchange-spring layer system. The depth dependence of the magnetization direction was determined by nuclear resonant scattering of synchrotron radiation from ultrathin 57Fe probe layers. In an external field a magnetic spiral structure forms that can be described within a one-dimensional micromagnetical model. The experimental method allows one to image vertical spin structures in stratified media with unprecedented accuracy. 相似文献
14.
C.T. Hsieh 《Applied Surface Science》2005,252(5):1899-1909
A magnetic force microscopy is used to examine the domain walls in nickel and cobalt films deposited by argon ion sputtering. Thin nickel films deposited at high substrate temperatures exhibit coexistent Bloch and Neel walls. Films grown at room temperature display alternative Bloch lines with cap switches. These films agglomerate to form grains after annealed at high temperatures. The film composed of larger grains behaves better nucleation implying magnetic domains of closure, while the film composed of smaller grains exhibits more defects implying alternative Bloch lines. We have also observed domain displacements and cap switches, which occur due to precipitation of particles in small grain size films. Stripe domains are observed for film thicknesses larger than 100 nm. They become zigzag cells when an external field of 1.5 T is applied perpendicular to the surface of the films. This experiment indicates that the domain sizes in thin films and the strip widths for thick films both depend on the square-root of the film thickness, which varies from 5 to 45 nm and from 100 to 450 nm, respectively. 相似文献
15.
A. A. Gavrilyuk A. V. Gavrilyuk I. L. Morozov N. V. Turik B. V. Gavrilyuk A. V. Semirov A. L. Semenov 《Russian Physics Journal》2008,51(2):182-187
Mechanisms of motion of the domain top separating oppositely magnetized domains through an amorphous ferromagnetic wire core
are investigated in an external magnetic field. The equilibrium parameters of the domain in the wire core are determined.
It is established that the character of motion of the domain top trough the wire core depends on the mutual orientation of
the external magnetic field and the domain magnetization. It is demonstrated that amorphous ferromagnetic wires based on transition
metals possess the magnetic diode effect.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 64–69, February, 2008. 相似文献
16.
S. Soriano C. Dufour K. Dumesnil Ph. Mangin 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):469-478
Below its ordering temperature (T
N
= 90 K), bulk bcc Eu has a helical magnetic state with propagation vectors along the three equivalent 〈100〉 directions. In
contrast, epitaxial (110)Eu films exhibit a unique magnetic ordering: the domain with a magnetic helix propagating along the
in-plane [001] direction vanishes on cooling, at the expense of other domains with helices propagating along [100] and [010].
This paper is devoted to the study of the stability of the magnetic domains in an external magnetic field using neutron scattering
experiments and macroscopic magnetization measurements. The helix propagating along the [001] direction can be restored by
the application of an external field along this direction. On the contrary, when a magnetic field is applied along an intermediate
direction, specifically [10], the domain with a helix propagating along [001] is suppressed. Both effects depend on the film thickness. They are explained
if one considers that, because of the low magnetic anisotropy of Eu, a helix with a propagation vector parallel to (or close
to) the applied magnetic field is energetically more favourable than cycloidal structures with unchanged propagation vectors.
Finally, the amplitudes of the propagation vectors and their directions (that are modified in films compared to bulk) do not
vary under magnetic field. 相似文献
17.
Below-diffraction-limited hybrid recording using silicon thin film super-resolution structure
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We report on new experimental results for
below-diffraction-limited hybrid recording. In our experiments, by
means of focused laser assisted magnetic recording, the magnetic
domains within TbFeCo thin films are obtained under an external
perpendicular direct magnetic field. For a single magnetic medium,
the domain size is mainly determined by the focused spot, which is
about 620~nm for the laser wavelength λ =406~nm, and
a numerical aperture of the lens of 0.80. However, when a silicon thin
film structure is inserted between the substrate and the magnetic medium,
the recording domains can be reduced obviously. By optimizing the
experimental condition, even the size can be reduced to about
100~nm, which is below the diffraction limit, i.e. about 1/6 of the spot
size. This is very useful for improving the hybrid recording density
in practical applications. 相似文献
18.
We have found that during giant magnetoresistance measurements in approximately 10 x 10 mm(2) NiFe/Cu/Co continuous film spin-valve structures, the resistance value suddenly drops to its absolute minimum during the NiFe reversal. The results reveal that the alignment of all magnetic domains in the NiFe film follow exactly that of corresponding domains in the Co film for an appropriate applied field strength. This phenomenon is caused by trapping of the NiFe domain walls through the magnetostatic interaction with the Co domain-wall stray fields. Consequently, the interlayer domain-wall coupling induces a mirror domain structure in the magnetic trilayer. 相似文献
19.
Botond Tyukodi Ioan-Augustin Chioar Zoltán Néda 《Central European Journal of Physics》2013,11(4):487-496
The topology and dynamics of stripe-like magnetic domains obtained in a ferrimagnetic garnet subjected to a time-dependent external magnetic field is studied experimentally and theoretically. Experiments are performed on a commercially available magnetic bubble apparatus, allowing the observation of the time-evolution of the magnetic domain structure. The system is modeled by a meso-scale Ising-type lattice model. Exchange and dipolar interactions between the spins, and interaction of the spins with the external magnetic field are considered. The model is investigated by kinetic Monte Carlo simulations with time-varying transition rates. In the limit of low temperatures the elaborated model leads to a magnetic domain topology and dynamics that is similar to the ones observed in the experiments. In the highly non-equilibrium limit with a high driving frequency the model reproduces the experimentally recorded hysteresis loops as well. 相似文献
20.
E. A. Vilkov 《Acoustical Physics》2005,51(5):524-532
The boundary-value problem of the magnetoelastic wave interaction with a moving domain wall in a ferromagnetic crystal is solved in the nonexchange magnetostatic approximation with allowance for the external magnetic field. It is shown that the difference introduced by magnetic field between the ferromagnetic resonance frequencies of the domains does not cause any noticeably departure of the refraction characteristics of reflected and transmitted waves from those observed at zero frequency mismatch. By contrast, the magnitudes of the transmission and reflection coefficients strongly depend on the external magnetic field and on the mobility of the domain wall. The dependence of the magnitude of the reflection coefficient on the external magnetic field at a fixed angle of shear wave incidence is found to possess two ferromagnetic resonance peaks. The positions and heights of the peaks may vary depending on the mobility of the domain wall. 相似文献