共查询到20条相似文献,搜索用时 53 毫秒
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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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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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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
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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
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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
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Li Zhang 《Journal of magnetism and magnetic materials》2010,322(18):2658-2664
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
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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
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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
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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
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D.J. Sellmyer Yingfan XuMinglang Yan Yucheng SuiJian Zhou R. Skomski 《Journal of magnetism and magnetic materials》2006
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
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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
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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
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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
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C.J. Sun Y.Z. Zhou J.S. Chen G.M. Chow G.H. Fecher H.J. Lin Y.K. Hwu 《Journal of magnetism and magnetic materials》2006
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