共查询到19条相似文献,搜索用时 93 毫秒
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提出了一个基于磁动力学方程的宏观唯象理论模型,对纳米级赝自旋阀结构的电流感应磁化翻转效应给出了明晰的物理解释:流入自由层的净自旋流和自由层内的自旋弛豫过程的共同作用,导致自由层总磁矩随时间的改变,甚至产生磁化方向的翻转.模型将“铁磁/非铁磁”界面的自旋相关散射,以及铁磁层中的自旋积累和弛豫过程,统一于宏观的磁动力学方程中.通过求解该方程的解析解,给出了赝自旋阀在电流激励下的磁化翻转条件和临界电流密度的表达式.对该效应的定性解释和数值模拟结果都和实验报道良好符合.根据模型分析了影响临界电流密度的诸因素,并指出提高器件性能的途径.
关键词:
电流感应磁化翻转
磁动力学方程
自旋电子学 相似文献
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自旋转矩临界电流过大的问题长期以来一直为人们所关注.本文提出,可以通过引入面外应力即引入应力各向异性场来降低退磁场,从而降低自旋转矩的临界电流.本文采用四分量分布式自旋电路模型计算了横向自旋阀由注入端输运到探测端(自由层)的极化电流大小.利用Landau-Lifshitz-Gilbert-Slonczewski方程数值研究了存在应力时,横向自旋阀中自旋转矩引起的自由层磁矩翻转的性质.结果表明,适当选择应力方向可使面外退磁场得到有效补偿,从而显著降低自旋转矩临界电流.另外,随着应力提高和退磁场的减小,磁矩翻转时间也大大减小. 相似文献
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本文详细介绍了单匝环路感应法的基本原理。结合电子技术和计算机测控技术,对该方法进行了改进,并应用该方法对Bi-2212超导筒的临界电流进行了研究,给出了实验结果。研究表明临界电流判据选取的越小,测量的系统误差越小。 相似文献
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从理论上研究了电流驱动磁开关中的热效应,在Neel-Brown弛豫时间理论和Li等的有效温度的工作基础上作了改进.在对称系综模型的Landau-Lifshitz-Gilbert和Fokker-Planck方程的基础上,分析了电流驱动磁动力学开关过程和电流引起磁势能的变化,提出一个新的电流感应磁势垒降低模型.新模型是非线性的,与Li等的有效温度模型不同.在此模型的基础上,讨论了开关临界电流对温度、开关时间的依赖关系,理论与实验相符合.对电流引起的样品温升的实验曲线进行了修正,实验结果与文中的非线性势垒降低模
关键词:
热效应
自旋传输矩
Neel-Brown弛豫时间
Fokker-Planck方程 相似文献
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以外加磁场压电悬臂梁能量采集系统结构为研究对象, 根据磁化电流方法探讨了具有悬臂梁特征的系统结构的磁场作用力及其计算方法, 给出了相应的磁力计算模型, 并将计算结果与实验数据进行了对比. 研究表明, 磁化电流方法导出的磁力计算模型存在偏差, 其磁力计算误差随着磁铁间距缩小而增大. 通过引入悬臂梁末端磁铁的偏转角度, 对磁化电流法计算模型进行改进, 得到合理的外加磁场压电悬臂梁能量采集系统的磁力计算模型, 为该能量采集系统的进一步研究提供了可靠的磁力计算理论依据. 相似文献
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利用线性自旋波方法并结合Hellmann-Feynman定理引入一种计算量子磁性系统临界磁场的方法.计算两种特殊模型的临界磁场,并将理论结果与数值结果进行比较,理论值与数值结果高度吻合,验证了理论方法的准确性. 相似文献
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We have investigated the current-induced magnetization switching in an exchange-biased spin valve structure. By using an unpatterned antiferromagnetic layer to pin the fixed Co layer, we obtained a lower switching current density by a factor of 5 than a simple spin valve structure. For the application, it is important to know how to keep the spin polarization when the thicker layer is pinned by an antiferromagnet. The unpatterned pinned ferromagnetic lead can be a good solution for spin-transfer-torque-activated device. The effect of Cu buffer layer on the top of the thin Co and Ru buffer layer under the thick Co layer on the current-induced magnetization switching in cobalt-based trilayer spin valves was also investigated. The experimental results showed that the Ru buffer layer in combination with Cu buffer layer could induce a decrease in the critical switching current by 30%, and an increase in the absolute resistance change by 35%, which is caused by an improvement of a microstructure of a thicker Co polarizer. 相似文献
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High critical current density ($> 10^{6}$ A/cm$^{2})$ is one of major obstacles to realize practical applications of the current-driven magnetization reversal devices. In this work, we successfully prepared Pd/CoZr(3.5 nm)/MgO thin films with large perpendicular magnetic anisotropy and demonstrated a way of reducing the critical current density with a low out-of-plane magnetic field in the Pd/CoZr/MgO stack. Under the assistance of an out-of-plane magnetic field, the magnetization can be fully reversed with a current density of about 10$^{4}$ A/cm$^{2}$. The magnetization reversal is attributed to the combined effect of the out-of-plane magnetic field and the current-induced spin-orbital torque. It is found that the current-driven magnetization reversal is highly relevant to the temperature owing to the varied spin-orbital torque, and the current-driven magnetization reversal will be more efficient in low-temperature range, while the magnetic field is helpful for the magnetization reversal in high-temperature range. 相似文献
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Hui-Zhong Xu Xiao Chen Jing Hua Jun-Ming Liu 《Journal of magnetism and magnetic materials》2009,321(22):3698-3701
Micromagnetic simulations based on the Landau–Lifshitz–Gilbert equation are presented to study spin-polarized current induced magnetization switching in asymmetric nanoring-shaped magnetic tunnel junctions. The results show that in a nanoring with an intermediate eccentric distance S, the critical switching voltage VC reaches the minimum whose magnitude is less than half of the voltage for a symmetric nanoring. In addition to the spin-transfer torque, the current induced Ampère field is found to play a crucial part in the switching process. Analysis is given to explain the existence of such an energy valley that leads to the minimal voltage. 相似文献
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Probing the magnetization switching with in-plane magnetic anisotropy through field-modified magnetoresistance measurement 下载免费PDF全文
Effective probing current-induced magnetization switching is highly required in the study of emerging spin-orbit torque(SOT)effect.However,the measurement of in-plane magnetization switching typically relies on the giant/tunneling magnetoresistance measurement in a spin valve structure calling for complicated fabrication process,or the non-electric approach of Kerr imaging technique.Here,we present a reliable and convenient method to electrically probe the SOT-induced in-plane magnetization switching in a simple Hall bar device through analyzing the MR signal modified by a magnetic field.In this case,the symmetry of MR is broken,resulting in a resistance difference for opposite magnetization orientations.Moreover,the feasibility of our method is widely evidenced in heavy metal/ferromagnet(Pt/Ni20Fe80 and W/Co20Fe60B20)and the topological insulator/ferromagnet(Bi2Se3/Ni20Fe80).Our work simplifies the characterization process of the in-plane magnetization switching,which can promote the development of SOT-based devices. 相似文献
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在用样品电流模式的测量过程中发现,磁场强度、磁场与样品表面的夹角以及光斑在样品表面的位置都会对吸收谱强度产生影响;在光斑、磁场和样品的不同几何配置下,测量并分析了表面均匀氧化的铝箔中氧的K边吸收谱,指出外磁场下吸收谱强度随各种条件变化的趋势,并对实验结果给出了合理解释;结果表明所用的模型分析与实验数据符合得很好;所得到的信息对于XMCD实验的设计安排、相应数据的分析以及物理信息的提取具有重要意义. 相似文献
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Y. Saito T. Inokuchi H. Sugiyama K. Inomata 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(4):463-469
We conducted a detailed study of hard axis magnetic field (Hhard)
dependence on current-induced magnetization switching (CIMS) in MgO-based
magnetic tunnel junctions (MTJs) with various junction sizes and various
uniaxial anisotropy fields. The decreases in critical current density
(Jc) and the intrinsic critical current density (Jc0) estimated from
the pulse duration dependence on Jc in CIMS are observed when applying
Hhard for all MTJs. The decrease in energy barrier of CIMS is also
observed except for the largest sample. These results indicate that the
reduction of Jc is attributable to both the increase of spin-transfer
efficiency and the decrease in energy barrier in the case of applying
Hhard. The Jc0 decreases with increase in the mutual angle between
the direction of magnetization and the easy axis (θf),
which is consistent with the theoretical prediction proposed by Slonczewski.
The degree of the reduction of Jc0 for the same value of Hhard
decreases with decreasing size of MTJs. This behavior is considered to be
related to not only decrease in θf due to the increase in
anisotropy field in MTJs, but also to the increase in the variance of the
initial angle of magnetization due to the thermally activated magnon
excitation. The stable switching endurance related to CIMS was observed in a
wide range of MTJ sizes when applying Hhard. Moreover, we proposed a new
architecture and a new switching method considering write disturbance. These
results would be useful for application to spin memory and other
spin-electronic devices. 相似文献
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Roles of spin-polarized current and spin accumulation in the current-induced magnetization switching
To clarify the contributions of spin-polarized current and spin accumulation to the current-induced magnetization switching, the effects of the top electrode size of the magnetic nanopillar are investigated both theoretically and experimentally. Theoretical calculation demonstrates that the spin-polarized current and the spin accumulation can be adjusted in opposite directions by modifying the size of the top electrode. Increase in the size of the top electrode suppresses the spin accumulation but enhances the spin-polarized current inside the nanopillar. On the other hand, it is shown experimentally that the nanopillar with a wide top electrode exhibits small critical switching current compared to the nanopillar with a narrow top electrode. The results suggest that the spin-polarized current contributes to the current-induced magnetization switching dominantly over the spin accumulation. 相似文献
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Vinod Prasad Shalini Lumb Talwar Sonia Lumb G. Lefkidis W. Hübner 《Physics letters. A》2019,383(26):125775
In this work we propose to study an atom confined in a potential which consists of a Hulthén potential plus a ring-shaped potential. The atom is further subjected to a spherical confinement. The time-independent Schrödinger equation (TISE) of the system is solved numerically. Exact energy levels are obtained. The persistent current and induced magnetic field of such a confined atom is evaluated. Finally, the atomic system in this potential and confinement is subjected to short electromagnetic pulses, which are shown to induce enormous currents. 相似文献
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分析两种均匀磁介质分界面上有长载流导线的场和电流分布,指出磁感应强度B=B(r)φ径向对称分布是由径向对称分布的总电流j=j(r)ez(包括传导电流和磁化电流)所激发,探讨了传导电流的分布与磁感应强度B、磁场强度H和磁化电流的分布的关系。 相似文献