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161.
Michelle J. S. Spencer Andrew Hung Ian K. Snook Irene Yarovsky 《Surface science》2003,540(2-3):420-430
The adsorption of atomic S on the Fe(1 1 0) surface is examined using density functional theory (DFT). Three different adsorption sites are considered, including the atop, hollow and bridge sites and the S is adsorbed at a quarter monolayer coverage in a p(2 × 2) arrangement. The hollow site is found to be the most stable, followed by the bridge and atop sites. At all three sites, S adsorption results in relatively minor surface reconstruction, with the most significant being that for the hollow site, with lateral displacements of 0.09 Å. Comparisons between S-adsorbed and pure Fe surfaces revealed reductions in the magnetic moments of surface-layer Fe atoms in the vicinity of the S. At the hollow site, the presence of S causes an increase in the surface Fe d-orbital density of states between 4 and 5 eV. However, S adsorption has no significant effect on the structure and magnetic properties of the lower substrate layers. 相似文献
162.
B. Pilawa I. Keilhauer G. Fischer S. Knorr J. Rahmer A. Grupp 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):321-330
The magnetic properties of the cyclic compound [Fe6(bicine)6] LiClO4
. 2MeOH are reported. The cluster Fe6(bicine)6 forms an antiferromagnetically coupled ring structure of Fe III ions. The magnetic susceptibility is measured between 2 and 300 K and yields the exchange coupling of J/k
B = - 27.5±0.5 K. The field dependence of the magnetic moment is studied at 3 and 6 K in magnetic fields up to 5 T. The zero-field
splitting of the first excited spin states with S = 2 and 3 are determined by ESR at 94 GHz. The intra-molecular interactions of the Fe III ions are analyzed and the on-site anisotropy of the Fe III due to the ligand-configuration is determined to d /k
B = - 0.633±0.008K.
Received 28 October 2002 / Received in final form 22 February 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: bernd@piobelix.physik.uni-karlsruhe.de 相似文献
163.
在多功能内耗仪上用自由衰减和强迫振动方法研究了Al含量对退火态Fe-Al合金Zener弛豫的作用.结果显示:中等Al含量的Fe-Al合金产生强的Zener弛豫,而较低和较高Al含量的Fe-Al合金只产生微弱的Zener弛豫峰.Fe-Al合金中的Zener弛豫产生于次近邻Al原子对的重新取向以及它们之间的相互作用,而不是来源于最近邻的Al原子对,后者因为形成短程有序结构不能产生Zener弛豫.
关键词:
Zener弛豫
Al含量 相似文献
164.
Based on a review of the current literature, a surface phase diagram is proposed for the submonolayer Au on Si(111) system. Kinetic considerations are reviewed and key surface phase diagram features such as the Θ < 0.4 ML metastable
structure and the high temperature
to Si(111)-(1 × 1)Au second order phase transition are discussed. Experiments to verify certain portions of the phase diagram are proposed. 相似文献
165.
Ranajeet Ghose James H. Prestegard 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1997,128(2):138-143
The effects of cross-correlation between Curie spin–nuclear dipole and nuclear dipole–nuclear dipole interactions on the linewidths and resonance frequencies of the individual lines of anAXmultiplet in paramagnetic systems have been calculated. The implication of the relaxation-induced frequency shift of the lines (dynamic frequency shift) for the accurate measurement of residual dipolar couplings in field-oriented systems has been discussed. Our simulations indicate that these effects may play a role in the precise measurement of residual dipolar couplings in systems which belong to the small and intermediate tumbling regime, i.e., correlation times less than 5 ns. 相似文献
166.
This study investigates ultra-thin potassium chloride (KCl) films on the Si(1 0 0)-2 × 1 surfaces at near room temperature. The atomic structure and growth mode of this ionic solid film on the covalent bonded semiconductor surface is examined by synchrotron radiation core level photoemission, scanning tunneling microscopy and ab initio calculations. The Si 2p, K 3p and Cl 2p core level spectra together indicate that adsorbed KCl molecules at submonolayer coverage partially dissociate and that KCl overlayers above one monolayer (ML) have similar features in the valance band density of states as those of the bulk KCl crystal. STM results reveal a novel c(4 × 4) structure at 1 ML coverage. Ab initio calculations show that a model that comprises a periodic pyramidal geometry is consistent with experimental results. 相似文献
167.
根据π电子的紧束缚模型,将电子的次近邻和第三近邻跳跃能考虑在内,得到扶手椅型石墨烯纳米带(AGRNs)能带结构的解析解.讨论了由次近邻和第三近邻电子跳跃引起的能带和能隙变化,发现次近邻和第三近邻跳跃分别对带隙产生增大和减小的影响. 比较了边界弛豫与非近邻跳跃之间的互相竞争关系. 当纳米带的宽度n为奇数时,二维石墨面的紧束缚模型中所固有的van Hove奇异性表现为AGRNs中的无色散带. 当AGRNs宽度增加时,能谱趋向于二维石墨烯时的能谱结构.
关键词:
扶手椅型石墨烯纳米带
非近邻跳跃
边界弛豫
电子结构 相似文献
168.
T. Bergmann M. DeKieviet T. Gasenzer O. Nachtmann M.-I. Trappe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):551-574
We discuss the propagation of hydrogen atoms in static electric and magnetic fields in a longitudinal atomic beam spin echo
(lABSE) apparatus. There the atoms acquire geometric (Berry) phases that exhibit a new manifestation of parity-(P-)violation
in atomic physics. We provide analytical as well as numerical calculations of the behaviour of the metastable 2S states of
hydrogen. The conditions for electromagnetic field configurations that allow for adiabatic evolution of the relevant atomic
states are investigated. Our results provide the theoretical basis for the discussion of possible measurements of P-violating
geometric phases in lABSE experiments. 相似文献
169.
Alena Juríková Kornel Csach Jozef Miškuf Václav Ocelík 《Central European Journal of Physics》2007,5(2):177-187
Creep strain recovery and structural relaxation of the amorphous metallic glass Fe40Ni41B19 after longtime loading at different annealing temperatures below the glass transition temperature have been studied using
anisothermal differential scanning calorimetry (DSC) and dilatometry (TMA). It has been demonstrated that structural relaxation
effects depend on the stress-annealing temperature of the amorphous ribbon. The structural relaxation states of the amorphous
ribbon annealed at different temperatures under and without applied stress have been compared. The activation energy spectra
were calculated from the anisothermal dilatometric measurements using the modern method based on the Fourier transformation
technique. The influence of the annealing temperature on the shape of creep strain recovery spectra has been analyzed.
相似文献
170.
Jing Chen Qiao-yan Dong Li-gang Zhang Bao-gen Shen 《Journal of magnetism and magnetic materials》2009,321(19):3217-3220
In NaZn13-type LaFe11.4Al1.6C0.02 compound, a signature of weak ferromagnetism is observed at ∼100 K under a low field by ac magnetic-susceptibility and electrical-resistivity measurements, implying the coexistence of ferromagnetic (FM) and antiferromagnetic (AFM) phases. The hysteresis in isofield magnetization curves and large magnetic relaxation demonstrate the metastability of the magnetic state in the AFM-FM transition region. The variations of magnetization with temperature, time and field show distinct step-like behaviors, which is probably attributed to the discontinuous growth of ferromagnetic cluster in antiferromagnetic matrix. 相似文献