Effect of Exchange Interaction Constants on the Magnetization Reversal in a Hard/Soft Magnetic Bilayer Model

Journal of Experimental and Theoretical Physics - A model is developed to study a hard/soft magnetic bilayer in an external magnetic field by the Monte Carlo method. The influence of the constants...     

Magnetization Reversal in Magnetic Bilayer Systems

Magnetization reversal in magnetic soft/hard bilayer systems is studied analytically by means of a variational method for magnetic energies in a continuum model. The demagnetization curve is involved with nonlinear equations,and the solution is given implicitly in the form of Jacobi functions,which is valid for the total reversal process. Based on the non-trivial solutions, hysteresis loops, as well as the maximum energy product(BH)_(max) versus thicknesses of soft/hard layers are obtained. With regard to(BH)_(max), improvement of the remanence competes with loss of coercive force. As a result, an optimum condition exists. For a given thickness of the hard layer, the optimum condition at which the largest(BH)_(max) could be achieved is discussed, which is slightly different from previous works.     

Influence of the Thickness of Gadolinium Layers on the Magnetic Properties and Magnetization Reversal Processes in Low-Dimensional Co/Gd/Co Systems

Physics of the Solid State - Structural and magnetic characteristics and behavior of thin-film Co/Gd/Co systems obtained by ion plasma sputtering in a magnetic field are reported. X-ray studies...     

基于Stoner-Wohlfarth 模型磁性纳米颗粒的磁化反转

纳米磁性材料由于其特殊的磁学性能,近年来,在许多领域受到了广泛的应用。在基础理 论研究中,人们提出了各种描述纳米磁性材料的理论;另一方面,计算机计算能力以及实验手段 的提高,使得应用计算机进行材料设计以及探测单个纳米颗粒的磁学特性成为可能。这使得人们 对纳米磁性材料的理解更加深入。本篇论文介绍了磁性纳米颗粒的磁化反转机制的基本理论与实 验研究的最新进展。本文首先从磁性材料中基本的相互作用入手说明这些相互作用在纳米尺度下 的表现形式,随后详细介绍了基于Stoner-Wohlfarth 模型计算机模拟方法,最后简单介绍两种 可以用来研究单个纳米颗粒磁化反转实验手段以及相关的实验结果。     

Effect of GMR and Magnetization Reversal on Microwave Absorption

Low-field microwave absorption has been measured as a function of magnetic field in a series of thin film structures exhibiting or not exhibiting the giant magnetoresistance effect (GMR). Although a close correlation has been found between the microwave absorption and GMR, an additional absorption due to magnetization reversal is shown to have substantial effect on the overall microwave response.     

Low-Temperature Magnetization Switching of Bilayer FeNi/FeMn Films

Journal of Experimental and Theoretical Physics - A change in the kinetics of magnetization reversal of a bilayer ferromagnet–antiferromagnet film during a decrease in the temperature is...     

Remanence Characteristic of Nanostructure of Hard／Soft Magnetic Multilayered Systems

The relation between microscopic properties (e.e.,layer thickness,easy axis orientation) and the macroscopic magnetic properties such as remanent magnetization of the ferromagnetic multilayer system is investigated based on a simple micromagnet approach.We concentrate on a multilayer design with periodic boundary condition,where alternating soft/hard layers build a nanostructured multilayer.For any easy axis direction in the soft and hard layers a simple explicit expression of remanence of the system has been derived analytically.We find that the remanence clearly depends on the thickness of the soft magnetic layer and is nearly independent of the thickness of hard magnetic layer.On the other hand,the remanence increases upon reducing the angle enclosed by the saturation magnetization and the easy axis directions of soft magnetic layer.However,it is unsensitive to the easy axis direction of hard magnetic layer,but there exists a maximum remanence for a certain easy axis direction of hard magnetic layer.     

Magnetization Reversal Studies of Magnetic Wire Arrays by Polarized Neutron Scattering

Polarized neutron reflectivity has been used to investigate the peak pattern and the magnetization reversal process of laterally structured Fe- and CoFe-films. The peak pattern of the wire arrays was analyzed in the specular as well as in the off-specular regime. The intensities of the different cross-sections at the off-specular first-order peak were investigated as a function of external magnetic field. Magnetization reversals are discussed and compared to MOKE studies of the same system.     

Field-and Current-Driven Magnetization Reversal and Dynamic Properties of CoFeB-MgO-Based Perpendicular Magnetic Tunnel Junctions

We report a perpendicular magnetic tunnel junction(p MTJ) cell with a tunnel magnetoresistance(TMR) ratio of nearly 200% at room temperature based on Co Fe B/Ta/Co Fe B as the free layer(FL) and a synthetic antiferromagnetic(SAF) multilayer [Pt/Co]/Ru/[Pt/Co]/Ta/Co Fe B as the reference layer(RL). The field-driven magnetization switching measurements show that the p MTJs exhibit an anomalous TMR hysteresis loop. The spin-polarized layer Co Fe B of SAF-RL has a lower critical switching field than...     

末端形状对NiFe纳米薄膜磁反转动力学特性的影响

基于微磁学模拟方法研究末端形状对NiFe纳米薄膜的磁反转和自旋波本征动力学特性的调制及磁反转与自旋波模式软化间的内在联系.纳米薄膜微磁结构的相变总是伴随着某种自旋波模式的软化,软化自旋波模式空间分布预示微磁结构相变的路径.存在一临界裁剪度（h₀）.当裁剪度h<h₀时,磁振荡局域于末端边缘的EM自旋波软化诱导磁反转从磁体末端边缘磁矩失稳开始,边缘失稳区域向中央扩展形成反转畴,最后反转畴逐渐移出膜面外而实现反转.当h≥h₀时,形状各向异性导致边缘局域化模式自旋波被抑制,反转场附近一致模式自旋波的软化诱导磁体一致反转.     

Comparison of the Hard and Soft Processes in High Energy Hadron-Hadron Colisions

Using the“con ealgorithm”in QCD to identify jet,the hard and soft processes in high energy hadroncic olisions are analysed indetail.A Monte Carlo simulation event sample is produced by PYTHIA.The resultant pseudorapidity distribution of jets has a plateau in the central region.The particle and transverse energy density in jets decreases exponentially with the increase of the distance from particles to jet axis.Through comparisons,we find the event average transverse momentum or maximum transverse momentum is positively correlated with multiplicity for the whole event sample,and negatively correlated with multiplicity for jet event subsample.Two ratio variables well describe the hardness of jet events,and they are positively correlated with the event average transverse momentum and negatively correlated with multiplicity,which confirms the event average transverse momentum is a better characteristic quantity to describe the hardness of jet events than multiplicity.     

Magnetization Reversal of Single-Molecular Magnets by a Spin-Polarized Current

We study the magnetization reversal of single-molecular magnets by a spin-polarized current in the framework of the spinor Boltzmann equation. Because of the spin–orbit coupling, the spin-polarized current will impose a non-zero spin transfer torque on the single-molecular magnets, which will induce the magnetization switching of the latter. Via the s–d exchange interaction between the conducting electrons and single-molecular magnets,we can investigate the magnetization dynamics of single-molec...     

Multistability of the Magnetization Reversal of a Nanoparticle with Cubic Anisotropy

JETP Letters - The dynamics of magnetization reversal of a nanoparticle with cubic magnetic anisotropy by a short Gaussian pulse of a magnetic field has been studied. It has been shown that the...     

高能强子–强子碰撞中硬软过程的比较分析

根据QCD中“圆锥定义”来确定喷注,对高能强子-强子碰撞中的硬、软过程作细致的分析.用Pythia产生蒙特卡罗模拟样本,得到的喷注赝快度分布在中心区有平台,喷注内部的粒子密度和横能密度,随离喷注轴的距离指数地下降,比较发现对整个事件样本,单事件平均横动量或最大横动量与多重数是正关联的,而对喷注事件它们是负关联的.引入两个物理量来描述喷注事件的硬、软程度.发现它们与单事件平均横动量是正关联的,而与多重数是负关联的.表明用单事件平均横动量比用多重数能更好地描述喷注事件的硬软程度.     

Reminiscence of a Magnetization Plateau in a Magnetization Processes of Toy-Model Triangular and Tetrahedral Clusters

Journal of Experimental and Theoretical Physics - We discuss magnetization curves of a toy-model trigonal and tetrahedral clusters. Nonlinearity of magnetization with local minimum of differential...     

Multistability of a Dipole Nanocell during Its Pulsed Magnetization Reversal

Physics of the Solid State - The dynamics of magnetization reversal of a nanocell composed of two magnetouniaxial nanoparticles by a short Gaussian magnetic-field pulse is investigated. This...     

Influence of Magnetization on the Spin Pumping Efficiency in a Ferromagnet–Normal Metal Bilayer Structure

The problem of spin current generation and transformation into electric signals in thin-film ferromagnet/nonmagnetic metal bilayer structures is investigated. This direction is of considerable scientific interest and promising for applications in spintronics. An LSMO/Pt structure consisting of an epitaxial film of ferromagnetic manganite La2/3Sr1/3O3 grown on a single-crystal NdGaO3 substrate and coated with a platinum film has been studied experimentally. The spin current was generated by the spin pumping method upon the excitation of a ferromagnetic resonance in the ferromagnetic layer and was detected by the electric voltage USP arising in the nonmagnetic metal layer due to the inverse spin Hall effect. Owing to its relatively low Curie temperature (~350 K), using LSMO allowed the influence of ferromagnetic-layer magnetization on the spin current generation to be studied in detail in the temperature range 100–350 K. In this case, the influence of the shape of the ferromagnetic resonance line, which is the convolution of homogeneous (Lorentzian) spin packets and inhomogeneous Gaussian broadening (Voigt model), was consistently taken into account. As a result of our analysis of all the parameters defining USP, we have obtained the temperature dependence of the mixed spin conductance, which has turned out to be approximately proportional to the ferromagnet magnetization squared. This result is compared with existing theoretical models.     

The Structure and Magnetic Properties of Fe-Cu-Nb-Si-B/Fe-Nb-Si-B Bilayer

We have investigated the structure (by TEM and SEM) and basic surface and bulk magnetic properties (by measurement of surface and bulk hysteresis loop and domain structure observations) of a Fe-Cu-Nb-Si-B/Fe-Nb-Si-B bilayer prepared by melt spinning method. We have detected perfect bonding between the two layers of the bilayered ribbon. This bonding produces tangential stress, which influences magnetic properties measured in surface layers at both sides of the ribbon.     

Dependence of the Magnetization Kinetics of Magnetic Dispersed Nanosystems on the Dispersed Phase Concentration and the Change of Its State

Russian Physics Journal - The paper presents the results of experimental investigation of the magnetization relaxation processes in an ensemble of magnetic nanoparticles. The experimental results...