Fen/Crn超晶格磁性和电子结构的第一性原理研究

采用基于密度泛函原理的全势线性缀加平面波方法(FLAPW),计算了超晶格Fen/Crn(n=1,3,5)的电子结构和磁性,结果表明铁磁耦合状态是基态,铁层的磁矩由于铬层的加入而有一些变化,铁层的磁矩随着n的增大而逐渐增强.铬层的磁矩的方向是正负相间变化的,相邻的铁层和铬层之间是反铁磁性耦合的,铁原子的d轨道和铬原子的d轨道在费米能附近有中等程度的杂化.     

BenLa (n=1—18) 团簇的结构、电子性质和磁性

采用基于密度泛函理论的第一性原理方法,在多种初始构型下充分考虑自旋多重度,研究了Be_nLa团簇的平衡几何结构、电子性质和磁性.结果表明：Be_nLa团簇的基态附近有许多能量非常接近的同分异构体,说明该团簇结构较复杂,对其基态的寻找极具挑战性.Be_nLa团簇具有磁性且稳定性远高于Be_n+1团簇,由此可知通过选择合适的掺杂元素可能得到高稳定性的磁性团簇.Be_{1 关键词： n}La团簇')" href="#">Be_nLa团簇 平衡几何结构 电子性质和磁性     

磁场控制技术在微流控芯片中的应用*

磁场作为除了电场和力场之外的另一个有力的驱动和控制手段,由于不需与溶液接触即可实现对被分析物的操纵,极大降低污染的可能,近年来被越来越广泛地用于微流控芯片系统,尤其在细胞、病毒甚至单分子的捕获、分选以及操纵等方面显示出较大优势。本文综述了微流控芯片系统中磁场控制技术的最新进展,分别从理论分析,磁场加工技术、泵阀的实现,微流体控制和磁分离等方面介绍了该领域近几年的发展状况,并重点分析了微流控芯片磁场操控技术在临床分析和现场检测方面的应用,及其未来发展趋势和需解决的主要问题。     

C掺杂Mn3Ge的电子结构和磁性

采用第一性原理计算方法研究C掺杂对Mn₃Ge的影响.对Mn_3-xGeC_x的晶体结构进行几何优化,发现C原子最稳定的掺杂位置在正八面体的中心位置.研究其电子结构和总磁矩随C掺杂量的变化,发现总磁矩随着C浓度的增加先减小后增大,其中Mn₃GeC_0.4总磁矩接近零,可以实现完全的磁性补偿.研究Mn₃GeC_0.4多层膜的磁性,给出总磁矩接近零的Mn₃GeC_0.4多层膜结构,为Mn₃Ge的实际应用提供参考.     

A Room-Temperature and Microwave Synthesis of M-Doped ZnO (M=Co,Cr, Fe,Mn &; Ni)

A room temperature and microwave method for the preparation M-Doped ZnO, where M=Co, Cr, Fe, Mn & Ni, is described. X-ray diffraction of the synthesized samples shows a single phase ZnO structure without any indication of the dopant. Magnetic studies of the as prepared samples show it to be paramagnetic. However, hydrogenation of particular samples at 573 K for 6 h resulted in transforming the samples to a room temperature ferromagnet.     

新超导体MgCNi3的虚晶掺杂研究

用全势线性缀加平面波方法,考虑局域自旋密度近似研究虚晶掺杂MgCNi₃的超导电性和磁性.计算了自旋极化能带结构、体弹性模量和它对压力的导数、原子磁矩m及其变化率.计算结果表明，对于电子掺杂的Mg_1-xAl_xCNi₃(0≤x≤0.5)，超导电性和磁涨落随掺杂量的增加逐渐减小.空穴掺杂的Mg_1-xNa_xCNi₃,在x＝0.12处出现铁磁相变，超导电性消失.在MgCNi₃少量空穴掺杂区域(0≤x<0.12)，表现为超导与磁涨落共存的不稳定状态. 关键词： 超导电性 能带结构 态密度 磁性     

Darstellung,Strukturen und Eigenschaften von SmBeF4 und SrBeF4 — ungewöhnliche Varianten der Barytstruktur

Preparation, Structures, and Properties of SmBeF₄ and SrBeF₄ – Unusual Variants of the Baryt Type Structure SmBeF₄ has been obtained as orange-yellow crystals and SrBeF₄ as colourless crystals while heating mixtures of SmF₃, Sm-powder, BeF₂ (2 : 1 : 3) and SrF₂ and BeF₂ (1 : 1), respectively, under Ar after 7–10 d at about 700°C. SmBeF₄ crystallizes in Pna2₁ (No. 33) with a = 846.1(5), b = 676.9(5), c = 524.1(4) pm and SrBeF₄ in P2₁/n (Nr. 14) with a = 529.5(5), b = 830.9(2), c = 678.8(4) pm and β = 90.0°. The structures of SmBeF₄ and the room temperature modification of SrBeF₄ are related to the baryt type structure. The differences to the structure BaSO₄ are mutual rotations of the BeF₄ tetrahedra and their shift with respect to the Sm and Sr framework, respectively. According to the refinement of the structure of SmBeF₄ at ?174°C these effects are enhanced at low temperatures. SmBeF₄ exhibits sharp luminescence lines at around 690nm. Measurements of the magnetic susceptibility show the temperature dependence typically found for Sm²⁺. The Madelung parts of the lattice energy for SmBeF₄ und SrBeF₄ have been calculated and discussed.     

On cobalt magnetization suppression at bimetallic interfaces

We study theoretically the Co magnetization suppression at the Co–M (M=Ti, Nb, Mo, Re, Os, Ir and Pt) interface. We consider (1) M(1×1) overlayer on the FCC(1 1 1) or HCP(0 0 0 1) slab, (2) c(2×2) Co–M alloy above the same surfaces. In the latter case, the Co magnetization is reduced to about 0.5 μ_B by Ti, Nb, Mo and Re, but the effect is probably an overestimation because of compression of M–Co bonds. At Co atoms below the M(1×1) overlayer, the Co magnetization does not drop below 1 μ_B. We discuss also the Co–M antiferromagnetic coupling.     

Magnetic Interactions in Insulating BEDT-TTF Salts

Inter-dimer magnetic interactions J in BEDT-TTF (bis(ethylenedithio)tetrathiafulvalene) salts in the Mott insulator regime are estimated from the intermolecular overlap integrals. The estimated J values are compared with the experimental results, and the stable spin alignment and the dimensionality of the spin systems are discussed.