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1.
We have computed electronic structures and total energies of circularly confined two-dimensional quantum dots and their lateral dimers in zero and finite uniform external magnetic fields using different theoretical schemes: the spin-density-functional theory (SDFT), the current-and-spin-density-functional theory (CSDFT), and the variational quantum Monte Carlo (VMC) method. The SDFT and CSDFT calculations employ a recently-developed, symmetry-unrestricted real-space algorithm allowing solutions which break the spin symmetry. Results obtained for a six-electron dot in the weak confinement limit and in zero magnetic field as well as in a moderate confinement and in finite magnetic fields enable us to draw conclusions about the reliability of the more approximative SDFT and CSDFT schemes in comparison with the VMC method. The same is true for results obtained for the two-electron quantum dot dimer as a function of inter-dot distance. The structure and role of the symmetry-breaking solutions appearing in the SDFT and CSDFT calculations for the above systems are discussed. Received 16 October 2001 and Received in final form 17 January 2002  相似文献   
2.
对以本征Si及重掺杂p型和n型Si作为中间层的Fe/Si多层膜的层间耦合进行研究,并通过退火,增大Fe,Si之间的扩散,分析界面扩散对层间耦合的影响. 实验结果表明,层状结构良好的制备态的多层膜,Fe,Si之间也存在一定程度的扩散,它是影响层间耦合的 主要因素,远远超过了半导体意义上的重掺杂,使不同种类的Si作为中间层的层间耦合基本 一致.进一步还发现,在一定范围内增大Fe,Si之间的扩散,即使多层膜的层状结构已经有了相当的退化,Fe/Si多层膜的反铁磁耦合强度基本保持不变. 关键词: Fe/Si多层膜 层间耦合 界面扩散  相似文献   
3.
Deák  L.  Bottyán  L.  Major  M.  Nagy  D. L.  Spiering  H.  Szilágyi  E.  Tanczikó  F. 《Hyperfine Interactions》2002,144(1-4):45-52
Hyperfine Interactions - Synchrotron Mössbauer Reflectometry (SMR), the grazing incidence nuclear resonant scattering of synchrotron radiation, can be applied to perform depth-selective phase...  相似文献   
4.
5.
Evaporative deposition at oblique incidence is shown to enhance the magnetic anisotropy of an Fe20Ni80 magnetic film and induce magnetic anisotropy in an overlying, strongly isotropic Fe70Co30 film. This deposition method for the formation of an underlayer of several lattice parameters in thickness and semi-hard overlayer of a few thousands Angstroms in thickness achieves a significant change in the magnetization process and strong suppression of the coercive forces of Fe70Co30 in the hard magnetization direction. Soft magnetization of the Fe70Co30 overlayer is not achieved when one of the layers is deposited at oblique incidence. It is anticipated that shape magnetic anisotropy is responsible in part for the magnetic anisotropy induced in both in Fe20Ni80 under- and Fe70Co30 overlayer by oblique incidence evaporation.  相似文献   
6.
Mössbauer spectroscopy with 57Fe (119Sn) probe layers is a useful method to study the local magnetic structures at buried interfaces. However interface alloying, which always exists in the real samples, have to be taken into account for accurate interpretation of experimental data. We developed an algorithm, which describes the interface intermixing in the multilayers. Substituting deposited atoms by atoms of substrate and floating of deposited atoms in the upper layers during epitaxial growth leads to the formation of asymmetric chemical and magnetic interfaces. This asymmetry in the M1/M2 superlattices can explain the difference between magnetic responses from M1 on M2 and M2 on M1 interfaces which were observed in experiments. Applying this intermixing model to the systems with probe layers located at different distances from the interfaces gives the natural explanation of hyperfine fields distributions on probe atoms and helps us clarify some discrepancies reported in the literature.  相似文献   
7.
Magnetic multilayers of 57Fe with nominal thickness, T nom, between 0.4 and 1.0 nm separated by 3.0 nm Al spacer layers were prepared by alternate deposition of the constituents in high vacuum. The samples were investigated at 4.2 K in external magnetic field. A fraction of Fe atoms corresponding to about 0.3 nm equivalent Fe-thickness was found to mix into the Al spacer. The extremely strong magnetic anisotropy observed for T nom < 0.8 nm is attributed to Fe layers of approximately two atomic planes thick. The anisotropy decreases considerably after the building up of the third Fe atomic layer starts at T nom = 0.8 nm, but full saturation was not achieved even for T nom = 1 nm and 3 T magnetic field applied perpendicularly to the sample plane.  相似文献   
8.
辣根过氧化物酶活性膜结构及生物电催化性能   总被引:3,自引:0,他引:3  
通过分子沉积法研究了在聚对苯二甲酸乙二醇酯(PET)表面及金电极表面组装辣根过氧化物酶(HRP)/聚对苯乙烯磺酸钠(PSS)多层生物活性膜,用原子力显微镜(AFM)研究了组装膜的表面形貌,并研究了组装膜的形貌、粗糙度和活性关系.应用循环伏安法(CV)研究了组装HRP膜后电极对H2O2的电化学催化还原作用.实验发现,采用亚甲基蓝(MB)溶液为介质,在H2O2浓度为0.2~5.0 mmol•L-1时,其响应电流对H2O2浓度变化基本呈线性.  相似文献   
9.
Core-shell colloidal particles were prepared with the core of monodisperse melamine formaldehyde particles (MF) with a diameter of 3.5 μm. The shell deposited on the core by the layer-by-layer (LbL) self-assembly was made with a copolymer ANp3 of 2-acrylamido-2-methylpropanesulfonate sodium (AMPS) and 3 mol% naphthalene label monomer and poly(diallyldimethylammonium chloride) (PD). Nonradiative energy transfer (NRET) from the naphthalene labels deposited on the MF particles to pyrene labels at a polyelectrolyte APy3, a copolymer of AMPS and 3 mol% pyrene label monomer, or to an ionic pyrene probe 1-pyrenemethylamine hydrochloride (PyMeA · HCl) in water was observed. The NRET efficiency was expressed as the emission intensity ratio I/I0 of naphthalene with and without existence of pyrene in the surrounding solution. With increasing pyrene concentration, I/I0 decreased down to about 0.2 and the mechanism for this NRET from the inner naphthalene label to the pyrene labels in solution is still ambiguous.  相似文献   
10.
《Electroanalysis》2003,15(20):1577-1583
Laccase enzymes from two different sources, namely, tree laccase from Rhus vernicifera and fungal laccase from Coriolus hirsutus were used for the development of biosensor for catechol. Laccase was immobilized onto the amine terminated thiol monolayers on gold surface by glutaraldehyde coupling. From the different thiol monolayers investigated, cystamine was found to be optimal with respect to sensitivity, stability, reproducibility, and other electrochemical properties of the enzyme electrode. Linear calibration in the range between 1 and 400 μM for catechol was obtained for fungal laccase covalently coupled on the electrode surface. The kinetic parameters determined using the Lineweaver‐Burk and Eadie‐Hofstee plots were Km=0.65 mM and Vmax=24.5 μA for fungal laccase compared to Km=5.4 mM and Vmax=6.6 μA for tree laccase on cystamine monolayer. The electrode showed good stability for 1 month without loosing appreciable activity when stored dry in a refrigerator at ?20 °C.  相似文献   
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