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331.
采用射频磁控溅射法在石英玻璃衬底上制备了ZnO:Mn薄膜, 结合N+ 注入获得Mn-N共掺ZnO薄膜, 进而研究了退火温度对其结构及室温铁磁性的影响. 结果表明, 退火后ZnO:(Mn, N) 薄膜中Mn2+和N3-均处于ZnO晶格位, 没有杂质相生成. 退火温度的升高 有助于修复N+注入引起的晶格损伤, 同时也会让N逸出薄膜, 导致受主(NO)浓度降低. 室温铁磁性存在于ZnO:(Mn, N)薄膜中, 其强弱受NO浓度的影响, 铁磁性起源可采用束缚磁极化子模型进行解释. 相似文献
332.
罗兰 《纯粹数学与应用数学》2012,28(3):313-328
主要研究带有Gilbert阻尼项的Landau-Lifshitz铁磁链方程的柯西问题.当初值的一阶导数适当小时,基于加权能量估计,证明了强解的整体存在性并且给出了解的最优的L2和L∞衰减估计. 相似文献
333.
P.A. Igoshev A.V. Zarubin A.A. KataninV.Yu. Irkhin 《Journal of magnetism and magnetic materials》2012
The quasistatic approximation and equation-of-motion decoupling for the electron Green's functions are applied to trace the effect of electronic dispersion and electron correlations on the ferromagnetism of two-dimensional itinerant-electron systems. It is found that next-nearest-neighbor hopping t′ is of crucial importance for ferromagnetism formation yielding the magnetic phase diagram which is strongly asymmetric with respect to half-filling. At small t′ in the vicinity of half-filling the ferromagnetic phase region is restricted by the spin-density wave instability, and far from half-filling by one-particle (spin-polaron) instability. At t′ close to t/2 ferromagnetism is stabilized at moderate Hubbard U due to substantial curvature of the Fermi surface which passes in the vicinity of the van Hove singularity points. The results obtained are of possible importance for high-Tc compounds and layered ruthenates. 相似文献
334.
Electronic structures and magnetism of Cu-doped zinc-blende ZnO have been investigated by the first-principle method based on density functional theory (DFT). The results show that Cu can induce stable ferromagnetic ground state. The magnetic moment of supercell including single Cu atom is 1.0 μB. Electronic structure shows that Cu-doped zinc-blende ZnO is a p-type half-metallic ferromagnet. The half-metal property is mainly attribute to the crystal field splitting of Cu 3d orbital, and the ferromagnetism is dominated by the hole-mediated double exchange mechanism. Therefore, Cu-doped zinc-blende ZnO should be useful in semiconductor spintronics and other applications. 相似文献
335.
In this paper, we have investigated Mn-doped SnO2 powder samples prepared by solid-state reaction method. X-ray diffraction showed a single phase polycrystalline rutile structure. The atomic content of Mn ranged from ∼0.8 to 5 at%. Room temperature M-H loops showed a ferromagnetic behavior for all samples. The ferromagnetic Sn0.987Mn0.013O2 showed a coercivity Hc=545 Oe, which is among the highest reported for dilute magnetic semiconductors. The magnetic moment per Mn atom was estimated to be about 2.54 μB of the Sn0.9921Mn0.0079O2 sample. The average magnetic moment per Mn atom sharply decreases with increasing Mn content, while the effective fraction of the Mn ions contributing to the magnetization decreases. The magnetic properties of the Sn1−xMnxO2 are discussed based on the competition between the antiferromagnetic superexchange coupling and the F-center exchange coupling mechanism, in which both oxygen vacancies and magnetic ions are involved. 相似文献
336.
337.
Masayoshi Seike Van An Dinh Kazunori Sato Hiroshi Katayama Yoshida 《Physica B: Condensed Matter》2012,407(15):2875-2878
We present a first-principles study of the magnetic properties of N-doped MgO, CaO and SrO, which have been proposed to constitute a new class of dilute magnetic semiconductors (DMSs) with no magnetic elements. In this study, it was found that under a homogeneously distributed condition, Curie temperatures could reach room temperature at sufficient N concentrations in the range of 20–30 at.%; however, an inhomogeneous N distribution in these DMSs is the favored configuration, which indicates that spinodal decomposition leads to a room-temperature blocking temperature at smaller N concentrations than those estimated for room-temperature ferromagnetism in the homogeneous distribution condition. 相似文献
338.
报道一种非常简单的制备NiO和Ni(OH)2空心微球的无模板水热法, 即通过NiCl2与氨水在140 ℃水热反应12 h, 制备了Ni(OH)2纳米片自组装的空心微球, 经400 ℃热处理2 h得到了NiO空心微球. 采用X射线衍射仪、扫描电镜和透射电子显微镜对产物进行表征, 并在室温下测试了它的磁学性能, 结果表明, Ni(OH)2空心微球的直径约为3~4 μm, 它是由尺寸1.1~1.3 μm左右的六方相结构的Ni(OH)2纳米片组装而成; NiO空心微球是由立方相纳米片和多孔纳米片组装而成, 它具有弱的铁磁性, 其矫顽力为583 Oe, 剩余磁化强度为0.213 emu/g. 研究了氨在Ni(OH)2纳米片的形成与组装过程中的作用, 提出了可能的生长机理. 相似文献
339.
340.
作为一种强磁场环境下的新概念动能武器,电磁轨道炮利用脉冲电磁力可加速宏观物体到超高速。然而,其导体内脉冲电流分布是不均匀的,严重时会影响轨道炮发射威力或发射可靠性。针对一种薄带状铜导体结构的复杂电磁轨道炮,根据导体内电流分布的邻近效应原理,提出了在铜导带两侧附加了铁护层的均匀电流方法,并建立了物理模型,利用商业软件对该模型进行了数值仿真,仿真分析结果表明:铁护层的加入,大幅提高了铜导体内电流均匀分布程度,提高了铜导体承载电流的能力。 相似文献