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1.
The plane-wave method is used to determine the spin-wave spectra in nanoscale one-dimensional magnonic crystals formed by
a periodic lattice of ferromagnetic stripes. The dynamic demagnetizing field in a new formulation is used in these calculations.
The calculated spectra of spin waves are compared with experimental data taken from literature and a good agreement is obtained.
The dependence of the spin-wave spectra on magnetic material parameters consisting of magnetic stripes is systematically studied.
We proved that the experimentally found magnonic band structure with two magnonic gaps is of magnetostatic nature. 相似文献
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C.H.O. Costa M.S. Vasconcelos P.H.R. Barbosa F.F. Barbosa Filho 《Journal of magnetism and magnetic materials》2012
In this work we carry out a theoretical analysis of the spectra of magnons in quasiperiodic magnonic crystals arranged in accordance with generalized Fibonacci sequences in the exchange regime, by using a model based on a transfer-matrix method together random-phase approximation (RPA). The generalized Fibonacci sequences are characterized by an irrational parameter σ(p,q), which rules the physical properties of the system. We discussed the magnonic fractal spectra for first three generalizations, i.e., silver, bronze and nickel mean. By varying the generation number, we have found that the fragmentation process of allowed bands makes possible the emergence of new allowed magnonic bulk bands in spectra regions that were magnonic band gaps before, such as which occurs in doped semiconductor devices. This interesting property arises in one-dimensional magnonic quasicrystals fabricated in accordance to quasiperiodic sequences, without the need to introduce some deferent atomic layer or defect in the system. We also make a qualitative and quantitative investigations on these magnonic spectra by analyzing the distribution and magnitude of allowed bulk bands in function of the generalized Fibonacci number Fn and as well as how they scale as a function of the number of generations of the sequences, respectively. 相似文献
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Since a decade photonic band gap research is expanding quickly and especially with self-assembled silica beads, called opals. However, a lot of problems are arising in their preparation, in particular the difficulty to produce large frequencies band gaps in common (periodic) silica photonic materials. To solve this problem quasiperiodic opals are known to be good candidates. Actually, the high degree of isotropy and the high homogeneity of Penrose tilings make them a good way to generate complete photonic band gaps. The aim of our group is to elaborate quasiperiodic photonic crystals by directed-assembly (dip-coating) on Penrose-like patterned surfaces (through electron beam lithography). We will briefly present the different elaboration steps of our opals. Thus, the patterning methods and the dip-coating system will be discussed with our recent results in dip-coated photonic crystals. 相似文献
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磁振子晶体是光子晶体或声子晶体在磁性材料领域内的替代品,是近来的一个研究热点. 本文提出了磁振子晶体领域内的一种平面波展开法,其较传统的平面波展开法能节约一半以上的计算时间. 采用此方法,数值计算了由Fe/EuO二种铁磁材料构成的二维磁振子晶体带结构. 数值计算结果表明,在一定的体积填充率下,有自旋波带隙的出现;影响磁振子晶体带隙结构形成的主要因素是有效场中的交换作用场,其他作用场的影响相对很小.
关键词:
磁振子晶体
带隙
平面波展开法 相似文献
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M. A. Morozova A. Yu. Sharaevskaya O. V. Matveev E. N. Beginin Yu. P. Sharaevskii 《Physics of Wave Phenomena》2016,24(1):1-6
A calculation model has been developed to describe the propagation of magnetostatic waves in a periodic structure consisting of two one-dimensional magnonic crystals, the periods of which are shifted relative to each other in the wave propagation direction. It is shown that, depending on the shift between the magnonic crystals, up to three bandgaps can be formed in this structure in the first Bragg resonance. 相似文献
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《Journal of magnetism and magnetic materials》2001,236(3):320-330
Propagation of spin waves (SWs) through a periodic multilayered magnetic structure is analyzed. It is assumed that the structure consists of ferromagnetic layers having the same thickness but different magnetizations. The wave spectrum obtained contains forbidden zones (stop bands) in which wave propagation is prohibited. Introduction into the structure of the ferromagnetic layer with a different thickness breaks the structural symmetry and leads to a localization of the SW mode with the frequency lying in the stop band. Reflection of the wave by the structure of the finite length and transmission of the wave through the structure are also investigated. Numerical calculations of the wave dispersion and the transmission coefficients for symmetrical periodic structures as well as the structures with a defect are presented. Drawing an analogy from photonic crystals known in optics, such magnetic structures can be called one-dimensional (1-D) magnonic crystals (MCs). The possibilities of existence of the 2-D MCs are also discussed. 相似文献
8.
A periodic structure in the form of two coupled magnonic crystals in which the coupling allows effective control of nonlinear effects during propagation of magnetostatic waves is examined. The main specific features of the nonlinear effects are revealed in comparison with the periodic structure in the form of one magnonic crystal. The ability of the nonlinear coupler to suppress high- or lower-power signals for the functional processing of microwave-frequency signals is demonstrated. 相似文献
9.
Optical properties of one-dimensional quasiperiodic crystals with a linear profile of the modulation parameters are studied. It is shown that such systems possess a wider photonic forbidden band than the ideally periodic systems. The asymmetric profile of variation of the system parameters leads to nonreciprocity, which allows one to use these systems as optical diodes. 相似文献
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Itinerant Topological Magnons in SU (2) Symmetric Topological Hubbard Models with Nearly Flat Electronic Bands 下载免费PDF全文
《中国物理快报》2021,(5)
We show that a suitable combination of flat-band ferromagnetism,geometry and nontrivial electronic band topology can give rise to itinerant topological magnons.An SU(2) symmetric topological Hubbard model with nearly flat electronic bands,on a Kagome lattice,is considered as the prototype.This model exhibits ferromagnetic order when the lowest electronic band is half-filled.Using the numerical exact diagonalization method with a projection onto this nearly flat band,we can obtain the magnonic spectra.In the flat-band limit,the spectra exhibit distinct dispersions with Dirac points,similar to those of free electrons with isotropic hoppings,or a local spin magnet with pure ferromagnetic Heisenberg exchanges on the same geometry.Significantly,the non-flatness of the electronic band may induce a topological gap at the Dirac points,leading to a magnonic band with a nonzero Chern number.More intriguingly,this magnonic Chern number changes its sign when the topological index of the electronic band is reversed,suggesting that the nontrivial topology of the magnonic band is related to its underlying electronic band.Our work suggests interesting directions for the further exploration of,and searches for,itinerant topological magnons. 相似文献
12.
The emergence of the self-modulation instability of monochromatic microwave spin waves excited in a periodic magnetic film structure, a magnonic crystal, has been observed. The magnonic crystal was fabricated by chemically etching the surface a single-crystal yttrium-iron garnet film. The self-modulation instability has been observed at the frequencies corresponding to the band gaps of the spin-wave spectrum of the magnonic crystal caused by Bragg resonances. Above a certain threshold value of the input microwave signal, the time profile of the output pulses corresponds to envelope solitons. 相似文献
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Effects of rotating noncircular scatterers on spin-wave band gaps of two-dimensional magnonic crystals 下载免费PDF全文
Using the plane-wave expansion method, the spin-wave band structures of two-dimensional magnonic crystals consisting of square arrays of different shape scatterers are calculated numerically, and the effects of rotating rectangle and hexagon scaterers on the gaps are studied, respectively. The results show that the gaps can be substantially opened and tuned by rotating the scatterers. This approach should be helpful in designing magnonic crystals with desired gaps. 相似文献
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David Ruelle 《Physica A》1982,113(3):619-623
We discuss the possibility that, besides periodic and quasiperiodic crystals, there exist turbulent crystals as thermodynamic equilibrium states at non-zero temperature. Turbulent crystals would not be invariant under translation, but would differ from other crystals by the fuzziness of some diffraction peaks. Turbulent crystals could appear by breakdown of long range order in quasiperiodic crystals with two independent modulations. 相似文献
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We report a theoretical investigation of the spin wave spectrum of a magnonic crystal with a defect. The latter is considered as either a single or double layer with parameters (the values of the uniaxial anisotropy and/or layer thickness) different from those of the constituent layers of the magnonic crystal. It is shown that, depending upon the parameters of the defect, the spectrum may contain either one or several additional discrete (localized) modes within the magnonic band gaps, or even a mini-band of those. 相似文献
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A. V. Drozdovskii A. A. Nikitin A. B. Ustinov B. A. Kalinikos 《Technical Physics》2014,59(7):1032-1035
Microwave properties of ferrite-ferroelectric magnonic crystals are investigated for the first time. The electric and magnetic rearrangement of the band gaps in the spectrum of proper electromagnetic spin waves in such structures is demonstrated. 相似文献
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This paper discusses nanomagnetic structures enabling the manipulation of propagating spin waves. We address in particular how domain walls, or more generally speaking inhomogeneous spin configurations, enhance the control of spin-wave transmission and thereby the functionality of magnonic devices. Three different microscopic mechanisms are outlined, considering an interference device, a spin-wave bus and a magnonic crystal. Inhomogeneous spin configurations are argued to shift the spin-wave phase, guide spin waves in nanochannels and allow for reprogrammable spin-wave band structures in periodic nanostructures, respectively. Such devices and functionalities are relevant for further developments in magnonics. 相似文献