共查询到19条相似文献,搜索用时 328 毫秒
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以氧化铝纳米孔为模板,采用直流电化学沉积的方法制备了Cd_(0.96)Zn_(0.04)S/Cd_(0.97)Mn_(0.03)S/Cd_(0.96)Zn_(0.04)S量子阱纳米线阵列,并系统研究了该纳米线阵列在不同温度和不同磁场下的电学输运特性.随着外磁场的变化,样品表现出共振传输特性.通过量子阱理论对实验现象进行了分析,直接得到了稀磁层Cd_(0.97)Mn_(0.03)S中s-d交换作用常数N_0α的定量结果.研究发现该交换作用常数随温度具有e~(-1/T)的变化趋势. 相似文献
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晶格振动和晶粒尺度对磁记录膜矫顽力的竞争影响研究) 总被引:1,自引:0,他引:1
对晶格自旋相互作用的交换积分进行了晶格振动的修正,依此修正,导出了振动对磁记录膜矫顽力的影响关系;分析了磁晶量子尺度效应对磁记录膜矫顽力的影响机制;讨论了振动效应和量子尺度效应相互影响,共同竞争的物理内涵.结果显示:①振动的存在将减小薄膜的矫顽力;②磁晶微粒的量子尺度效应将使薄膜的矫顽力增加;③振动效应和量子尺度效应相互影响,共同竞争,为薄膜提供矫顽力;④要提高薄膜完备系的矫顽力,可将磁记录膜制成纳米级薄膜. 相似文献
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采用能量极小原理的微磁学及Monte Carlo方法对铁磁/反铁磁混合磁性薄膜的磁特性进行了模拟计算,研究了基态下系统的磁滞回线、自旋组态及铁磁交换作用常数JAA、单轴各向异性常数K、偶极相互作用常数D和铁磁性原子掺杂量X对矫顽力Hc的影响. 同时还模拟计算了矫顽力Hc的温度特性.模拟结果表明,在混合磁性薄膜中磁滞回线存在明显的阶梯效应,利用简单的Ising模型揭示这种阶梯效应主要起源于包含不同反铁磁原 子的掺杂量的不同尺寸的原子团对外加磁场所产生不同响应;在基态下当0.5≤X≤1.0时矫顽力Hc随K,J
关键词:
蒙特卡罗
微磁学
阶梯效应
混合磁系统
矫顽力 相似文献
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<正>研究了缀饰格子中的量子自旋霍尔效应,模型中同时考虑了Rashba自旋轨道耦合和交换场的作用.缀饰格子具有简立方对称性,以零能平带和单狄拉克锥结构为主要特点.在缀饰格子中,不论是实现量子自旋霍尔效应还是量子反常霍尔效应,都需要一个不为零的内禀自旋轨道耦合作用来打开一个完全的体能隙,这与石墨烯等六角格子模型有着很大的不同.在交换场破坏了时间反演对称性的情况下,以自旋陈数为标志的量子自旋霍尔效应仍然能够存在,边缘态和极化率的相关结果也证明了这一结论.结果表明自旋陈数比z2拓扑数在表征量子自旋霍尔效应方面有着更广泛的适用范围,相应的结论为利用磁场控制量子自旋霍尔效应提出了一个理论模型和依据. 相似文献
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通过微磁学模拟的手段对用电化学沉积法制备出的呈圆柱形的铁纳米线在常温下的磁行为进行了系统的研究,结果表明不同形状参量的铁纳米线都表现出磁各向异性,矫顽力随纳米线直径变化近似呈现平方反比关系,而对每一固定的直径,矫顽力随纳米线长度的增加而增大,最后趋向定值.磁滞回线形状、静态磁矩分布和反转机制等都随纳米线的直径和长度的变化而变化,对相应的规律给出了明确的解释.模拟结果显示实验上尚不能制备出的直径为5nm的纳米线呈现一致反转机理,同时还发现当纳米线过渡为颗粒时表现出更为复杂的性质
关键词:
纳米线
微磁学 相似文献
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用自旋动力学方法系统地研究磁偶极相互作用表现的边界效应对小尺寸正方形铁磁薄膜的磁化翻转过程的影响.在确定的磁偶极相互作用强度下,针对不同的单轴各向异性强度和不同的磁化角(外磁场与易轴间的夹角),具体给出矫顽场与磁化角及单轴各向异性强度之间的依赖关系和-些有代表性的磁滞回线,并给出磁化翻转过程中-些有代表性的微观磁结构.模拟结果表明:磁偶极相互作用表现的边界钉扎作用与单轴各向异性场之间的竞争决定磁滞回线的形状和矫顽场的大小,从而在不同磁化角情况下会导致不同的矫顽场机理.本文提出可有效地描述正方形铁磁性薄膜复杂微观磁畴结构的形成与演变的五磁畴模型.这种五磁畴模型既能直接揭示单轴各向异性正方形铁磁薄膜的几何特性和物理特性,也方便于磁化翻转过程的分析. 相似文献
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The magnetization and susceptibility of a cylindrical core/shell spin-1 Ising nanowire are investigated within the effective-field theory with correlations for both ferromagnetic and antiferromagnetic exchange interactions between the shell and the core. We find that the nanowire system exhibits two distinct susceptibility peaks and two successive phase transitions; either both of them are second-order transitions or one is a second-order transition and the other is a first-order transition for a small exchange interaction. The susceptibility versus switching field and the hysteresis behavior are investigated for different temperatures. It is found that the magnetization reversal events appear as peaks in the susceptibility versus switching field curve, the positions of which define the coercive field points of the nanowire system; the distance between the two susceptibility peaks decreases with increasing temperature. 相似文献
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A. A. Ivanov V. A. Orlov M. V. Erementchouk N. N. Podolsky 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(1):83-91
The process of quasistatic displacement of domain walls is
considered in a nanowire represented as a one-dimensional chain of
ferromagnet crystallites. The domain wall pinning due to spatial
fluctuations of the anisotropy axes is analyzed. Based on the theory
of overshoots of random processes, we have calculated the
distribution functions of the initial susceptibility and of the
maximal force of interaction of the domain wall with inhomogeneities.
These functions are found to be non-Gaussian. We have derived
expressions for the magnetization curve and the coercive force, which
depend on the length of the chain. 相似文献
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Magnetic nanowire arrays in anodic alumina membranes: Rutherford backscattering characterization 总被引:1,自引:0,他引:1
M. Hernández-Vélez K.R. Pirota F. Pászti D. Navas A. Climent M. Vázquez 《Applied Physics A: Materials Science & Processing》2005,80(8):1701-1706
Systematic study of magnetic nanowire arrays grown in anodic alumina membranes (AAM) has been done by means of Rutherford backscattering spectroscopy (RBS). The AAM used as templates were morphologically characterized by using high resolution scanning electron microscopy (HRSEM), fast Fourier transform (FFT) and atomic force microscopy (AFM). The highly ordered templates with a mean pore diameter size of 30 nanometers, a mean inter-pore spacing of 100 nm and lengths ranging from 4 to 180 microns were obtained through two-steps anodization process, and the Ni and Co nanowire arrays were grown by electrodeposition techniques. The main attention is addressed to Ni nanowire arrays. RBS results allowed us to determine the real depth profile of atomic composition of the obtained nanowire arrays. In addition, the RBS spectra fitting showed that the porosity increased from the top to the bottom of the samples. Two phenomenological models are proposed to understand the apparition of that secondary porosity and a linear relation between the total amount of electrodeposited Ni and the electrodeposition time was obtained. As an example, it is also reported the relation between RBS results and magnetic properties, such as coercive field and remanence/saturation magnetization ratio of the samples. Particularly, for Ni nanowires arrays obtained by using voltage pulses, it is demonstrated that the larger the nanowires, the higher the definition for easy axis parallel to the nanowire length is possible. PACS 82.80.Yc; 81.16-c; 75.75.+a 相似文献
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利用交流电化学沉积方法在氧化铝模板中制备了一维结构的FexCo1-x(0 ≤ x ≤ 0.51)二元合金纳米线阵列.X射线衍射结果显示,单质Co纳米线为(100)择优取向的hcp结构,FeCo合金纳米线则呈现(110)择优取向的bcc结构,而且衍射峰随纳米线中Fe含量的增加向低角度偏移.室温磁性测量结果显示, FeCo合金纳米线具有较好的磁特性.与Co纳米线相比,Fe的引入改善了Co纳米线的磁性能,使其呈现出较大的矫顽力和较高的矩形比.采用一致转动模型和对称扇形机理的球链模型分别计算了FeCo合金纳米线的矫顽力, 发现其磁化反转机理与对称扇形机理的球链模型相符合. 相似文献
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We study the spin Nernst effect of a mesoscopic four-terminal cross-bar device with the Rashba spin–orbit interaction (SOI) in the absence of a magnetic field. The interplay between the spin Nernst effect and the seebeck coefficient is investigated for a wide range of the Rashba SOI. When no peaks appeared in the seebeck coefficient, an oscillatory spin Nernst effect still occurs. In addition, the disorder effect on the spin Nernst effect is also studied. We find that the spin Nernst effect can be enhanced up to threefold by disorder. Besides, due to the interface effect, the counter propagating of the charge current to the direction of the temperature gradient is possible for a nonuniform system. 相似文献
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The coercive force is calculated for a rigid and a one- or two-dimensionally vaulted Bloch wall on the basis of a statistical theory. It is shown that the validity of the various pinning models developed previously depends on the defect density, the interaction force, and the area and flexibility of the domain wall. Our theoretical results are confirmed by a computer simulation of the pinning problem. The study of the temperature dependence of the coercive force proves to be a sensitive test to decide which pinning model applies. 相似文献
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A comparative analysis of the influence of random fluctuations of the crystallographic anisotropy and surface roughnesses
on the pinning of a domain wall in a nanowire has been performed in the framework of the model of a polycrystalline nanowire.
The initial magnetization curve and the coercive force for these mechanisms of pinning have been calculated. A criterion has
been formulated according to which surface inhomogeneities of the nanowire play the key role in the process of pinning of
a domain wall. The analytical results obtained have been verified using computer simulation. 相似文献