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1.
通过电阻应变片法得到其磁致伸缩系数随磁感应强度的变化关系.由磁滞回线以及磁导率随磁场变化关系可以得到该Fe-Ga磁致伸缩材料为软磁材料,几乎没有剩磁、矫顽力.  相似文献   

2.
翁臻臻  冯倩  黄志高  都有为 《物理学报》2004,53(9):3177-3185
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   

3.
江建军  袁林  邓联文  何华辉 《物理学报》2006,55(6):3043-3048
用微磁学方法对磁性纳米颗粒膜的磁特性进行了模拟,采用的模型是由122个磁性纳米颗粒组成的面心立方(fcc)结构体系.结果表明:在该体系中,偶极相互作用对体系的静态磁结构的影响显著,而交换相互作用的影响表现不明显.在此基础上,本文还采用有效媒质理论计算分析了磁性合金颗粒不同体积比时颗粒膜的磁谱和表征电磁参量发生显著变化的逾渗现象和逾渗阈值.并完成了对高磁损耗磁性纳米颗粒膜的材料设计. 关键词: 微磁学 纳米颗粒膜 逾渗阈值 磁导率 材料设计  相似文献   

4.
铁纳米线磁行为的微磁学模拟与研究   总被引:16,自引:0,他引:16       下载免费PDF全文
肖君军  孙超  薛德胜  李发伸 《物理学报》2001,50(8):1605-1609
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   

5.
二维无规混合磁性系统磁特性的微磁学及Monte Carlo研究   总被引:5,自引:2,他引:3  
采用能量极小原理的微磁学及Monte Carlo方法对异类自旋组成混合Heisenberg自旋体系进行模拟计算,研究了二维铁磁反铁磁无规混合系统的磁特性.发现了二维无规混合磁性系统存在M-H磁化曲线的阶梯效应.通过一维Ising模型及系统能量、自旋组态的研究,发现小自旋数目的反铁磁耦合系统是产生M-H阶梯效应的根本原因.  相似文献   

6.
Co纳米线磁矩反转动态过程的有限元微磁学模拟   总被引:2,自引:0,他引:2       下载免费PDF全文
采用有限元微磁学模拟方法研究了Co纳米线在不同外加恒磁场下磁矩的翻转过程.研究结果表明在直径为10 nm的Co纳米线内,经过一定的形核时间将在其一端形成一个反向磁畴.磁畴壁的类型为横向畴壁,该畴壁将在一外加恒定磁场的驱动下匀速地从一端运动到另一端.畴壁的运动速度与外加磁场大小呈线性关系.在H为1000 kA/m时,发现在纳米线的两端均会形成一个“头对头”的反向磁畴.计算结果表明,畴壁内磁矩的方向旋转一个周期所导致的畴壁运动的距离相同,与外加磁场强度无关. 关键词: 磁性纳米线 微磁学模拟 磁畴 横向畴壁  相似文献   

7.
杜海峰  杜安  胡勇 《计算物理》2006,23(5):583-588
采用类Ising模型,利用Monte Carlo方法研究了磁性单层膜中退磁性偶极作用和铁磁性交换作用对系统磁学性质的影响.结果显示,随着偶极相互作用的增加,系统在低温下的磁化出现平台现象,此时磁化曲线可分为2个阶段,在低外场下,温度升高,系统易磁化,在高外场下则反之.这种新奇的磁化行为导致系统的磁熵变在低温低外场下出现大于零的反常行为.在模拟过程中,对长程力作用采用了比较精确的处理方法.  相似文献   

8.
杨芝  张悦  周倩倩  王玉华 《物理学报》2017,66(13):137501-137501
磁性薄膜磁学特性电场调控的相关研究对开发新型低功耗磁信息器件具有突出意义.本文基于电场调控磁性的基本理论,以OOMMF(Object Oriented Micro-Magnetic Frame)微磁学仿真软件为工具,研究了电场对生长于PZN-PT单晶衬底上Fe_3O_4单晶薄膜磁学特性的调控.研究结果显示:无外加电场时,薄膜表现出典型的软磁特性;沿衬底[001]方向施加的外加电场可以使得薄膜矫顽力、矩形比等磁学特性发生显著改变:当外加磁场沿[100]([010])时,施加正值(负值)电场强度可以显著增大薄膜的矫顽力与矩形比,当电场强度不小于0.6 MV/m时薄膜矩形比达到1.这是因为外加电场导致薄膜产生单轴应力各向异性,使得薄膜的等效磁各向异性发生了从无外电场下的面内四重磁晶各向异性向高电场下的近似单轴磁各向异性的过渡.外加1 MV/m与-1 MV/m的电场时等效易磁化轴分别沿[100]与[010]方向.另外,外加1 MV/m(-1 MV/m)的电场强度可以使得铁磁共振的频率增大(减小)接近1 GHz.  相似文献   

9.
金晨东  宋承昆  王金帅  王建波  刘青芳 《物理学报》2018,67(13):137504-137504
磁斯格明子作为一种具有拓扑保护性质的准粒子受到了磁学与磁性材料领域科学家的广泛关注.本文对磁斯格明子的拓扑性质进行了概述,回顾了磁斯格明子的存在条件以及运输特性,综述了近年来利用微磁学模拟研究的磁斯格明子激发、操控、微波磁场响应以及基于磁斯格明子的器件设计,主要包括赛道存储器、自旋纳米振荡器、晶体管和逻辑门.通过本文的综述,希望为磁斯格明子在未来信息领域的应用提供参考.  相似文献   

10.
涂宽  韩满贵 《物理学报》2015,64(23):237501-237501
本文基于微磁学理论模拟了多孔α-Fe纳米片的微波磁性能. 与无纳米孔洞的纳米片对比, 发现由于纳米孔洞的引入导致退磁能发生改变, 破坏了纳米片原有的磁畴分布, 使纳米片内部存在数目更多、体积更小、局域有效场强不同的磁畴, 从而增加了高频磁损耗峰的数目. 由于部分损耗峰的相互交叠, 为在10–30 GHz范围拓宽电磁波吸收的带宽提供了潜在可能性. 模拟结果表明多孔纳米片的磁损耗峰数目、强度、峰宽和频率分布受孔洞排布方式和孔洞数目的影响. 由于纳米孔洞的存在可以降低材料的密度, 模拟结果表明多孔α-Fe纳米片可用于开发吸收频段宽、重量轻的电磁波吸收材料.  相似文献   

11.
We report (FePt)Ag-C granular thin films for potential applications to ultrahigh density perpendicular recording media, that were processed by co-sputtering FePt, Ag, and C targets on MgO underlayer deposited on thermally oxidized Si substrates. (FePt)1−xAgx-yvol%C (0<x<0.2, 0<y<50) films were fabricated on oxidized silicon substrates with a 10 nm MgO interlayer at 450oC. We found that the Ag additions improved the L10 ordering and the granular structure of the FePt-C films with the perpendicular coercivity ranging from 26 to 37 kOe for the particle size of 5-8 nm. The (FePt)0.9Ag0.1-50vol%C film showed the optimal magnetic properties as well as an appropriate granular morphology for recording media, i.e., average grain size of Dav=6.1 nm with the standard deviation of 1.8 nm.  相似文献   

12.
A new technique, which utilizes the interlayer diffusion, for preparation of self-assembled nanodot magnetic structures has been proposed. L10-phase Pt/FeCu and Pt/FeAg films have been successfully synthesized by this technique. Both the coercivity of Pt/FeCu and Pt/FeAg films exhibited, respectively 4.1 and 8.0 kOe in perpendicular direction. Pt/Fe and Pt/FeAg films show positive values, while Pt/FeCu shows negative value in δm plot. The results indicate that the exchange coupling between the grains has been decoupled in the self-assembled nanodot structure in Pt/FeCu film.  相似文献   

13.
Wei Jiang  Veng-cheong Lo  Jun Yang 《Physica A》2010,389(11):2227-1047
A molecular-based magnetic material AFeIIFeIII(C2O4)3 (A = organic cation) with a honeycomb structure is studied. The molecular-based magnet system consists of mixed spin-2 and spin- 5/2 honeycomb lattices with ferrimagnetic interlayer coupling. The magnetization, hysteresis loops and initial susceptibility have been calculated using a numerical method which includes both the longitudinal and transverse fields. We investigated the magnetic reversal of the system and found the existence of triple hysteresis loop patterns, affected by the anisotropy, longitudinal and transverse fields, and interlayer and intralayer exchange.  相似文献   

14.
15.
肖嘉星  鲁军  朱礼军  赵建华 《物理学报》2016,65(11):118105-118105
具有超强垂直磁各向异性的L10-MnxGa薄膜由于其与半导体材料结构及工艺的高度兼容性而受到广泛关注, 其超高垂直磁各向异性能和极低的磁阻尼因子预示着L10-MnxGa薄膜在高热稳定性自旋电子学器件中将发挥重要作用. 而L10-MnxGa超薄膜对于降低L10-MnxGa基垂直磁各向异性隧道结中的磁矩翻转临界电流密度有着重要的意义. 本文采用分子束外延的方法, 在半导体GaAs衬底上成功制备出了一系列不同厚度的L10-Mn1.67Ga薄膜, 厚度范围为1-5 nm. 生长过程中反射式高能电子衍射原位检测以及X射线衍射结果均表明了其良好的单晶相. 磁性测量结果表明, 厚度在1 nm以上的L10-Mn1.67Ga薄膜均可以保持垂直磁各向异性特征, 厚度为5 nm的L10-Mn1.67Ga薄膜的垂直磁各向异性能可达到14.7 Merg/cm3. 这些结果为基于L10-Mn1.67Ga的垂直磁各向异性隧道结在自旋转移扭矩驱动的磁随机存储器等低功耗器件的集成及应用提供了重要的实验支持.  相似文献   

16.
In this paper we report results on the synthesis and magnetic properties of L10 FePt nanocomposite films. Three fabrication methods have been developed to produce high-anisptropy FePt films: non-epitaxial growth of (0 0 1)-oriented FePt:X (X=Ag, C) composite films that might be used for perpendicular media; monodispersed FePt(CFx) core–shell nanocluster-assembled films grown with a gas-aggregation technique and having uniform cluster size and narrow size distribution; and template-mediated self-assembled FePt clusters prepared with chemical synthesis by a hydrogen reduction technique, which has a high potential for controlling both cluster size and orientation. The magnetic properties are controllable through variations in the nanocluster properties and nanostructure. Analytical and numerical simulations have been done for these films, providing better understanding of the magnetization reversal mechanisms. The films show promise for development as magnetic recording media at extremely high areal densities.  相似文献   

17.
测量了居里点为TC=220K的钙钛矿(La0.2Nd0.8)0.67Pb0.33MnO3 (LNPMO)在外场为ha=3978.87A/m ,2K相似文献   

18.
A three-dimensional micromagnetic model with non-uniform grain size distribution has been built up to study the magnetization process in FePt L10 perpendicular media. A 3D model of a single FePt magnetic grain is also set up for comparison. The high magneto-crystalline anisotropy Ku results in a short exchange length lex in FePt nanograins. Therefore a magnetic grain is divided into smaller grids on the order of lex. The simulated perpendicular and longitudinal loops are consistent with experiments, and it is explained why the measured perpendicular Hc is relatively smaller compared with the saturation field of the longitudinal loop in the FePt perpendicular medium.  相似文献   

19.
Granular L10 FePt (0 0 1) thin films were deposited on a Si substrate with Ta/MgO underlayers by rf sputtering. The effects of in-situ heating temperatures (350-575 °C), pressures (2-40 mTorr), and sputtering powers (15-75 W) on texture and microstructure were investigated for the FePt films. We obtained films with grain densities approaching 50 teragrains per in.2, grains sizes down to 2.2 nm with center-to-center spacing of 4.2 nm and coercivity of 24 kOe. The order parameters for the L10 FePt thin films were derived and calculated to be as high as 0.91. Although the grain size is small, the spacing between grains is too large for practical heat assisted magnetic recording media. To reach the desired results, we propose that layer-by-layer growth should be promoted in the FePt layer by inserting another underlayer that provides a better lattice match to L10 FePt.  相似文献   

20.
The field dependence of spin and orbital magnetic moments of Fe in L10 FePt magnetic thin films was investigated using X-ray magnetic circular dichroism (XMCD). The spin and orbital moments were calculated using the sum rules; it was found that the spin and orbital moment of Fe in L10 FePt films are ∼2.5 and 0.2 μB, respectively. The relative XMCD asymmetry at Fe L3 peak on the dependence of applied field suggested that the majority magnetic moment of L10 FePt films resulted from Fe.  相似文献   

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