铁纳米线磁行为的微磁学模拟与研究

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     

π和σ体系彻底分离的高度定域的键轨道基组的建立

高度定域的、对称的、键轨道基组的建立是一个多步的计算程序：(1)以定域片断轨道[φk,φi,φj]为基,对分子作有条件的RHF运算,算得FUL和DSI°态的片断分子轨道[Φ°l',Φ°n,Φ°m]和[Φl,Φn,Φm]。在基组[φk,φi,φj]中,φi∈双占据和空σ片断分子轨道(FMOs)组,φj∈πFMO组,φk∈单占据σFMO组,它们都精确地定域在各自的片断内;(2)利用Φ°l'与Φ°l间的重叠积分值(Sl'l>0.5),可以从DSI°态中,自动地选出Ns个对称的、由单占据轨道线性组合而成的分子轨道Φ°l'=Σakl'φk(k=1,2,…,Ns),接着,用Φ°l'取代FUL态中同类的、非对称轨道组Φl=Σaklφk(k=1,2,…,Ns);(3)以上述新的轨道组[Φ°l',Φn,Φm]为基(其中,Φ°l'∈DSI°态,它们离域于整个分子;双占据及空σFMO组Φm和πFMO组Φm属于FUL态),按FUL态的条件,再次对分子作有条件的RHF运算,从中得到一组对称的、闭壳层正则FMOs,而且每一个FMO均有正确的电子占据数;(4)利用Perkin原理,将第3步所得的正则FMO组定域成一个对称的键轨道基组[Φl',Φn',Φm']。在这个基组中,π体系Φm'与σ构架Φn'是彻底分离的,而且这两个轨道组始终精确地定域在各自的片断内。     

N-苄叉基-2-氨基噻唑及其类似物的构象和分子内的扭曲驱动力

确定了N-苄叉基-2-氨基噻唑(2a)和N-对硝基苄叉基-2-氨基噻唑(2b)的晶体结构.结合已报道的N-对硝基苄叉基-2-氨基嘧啶(1a),N-对硝基苄叉基-2-氨基吡啶(1b)和N-苄叉基-3-氨基吡啶(2c)的晶体结构,利用AM1,RHF,DFT方法和6-311G,6-311G^**基组,优化每个分子的22个旋转构象(θ=0°～90°).由DFT法所得到的最优构象的扭角θ(1a,22°;1b,0°;1c,42°;2a、2b:0°)与实验值(1a,26°;1b,20°;1c,46°;2a,8.8°;2b,3.8°)最接近.尽管分子最优构象扭角的差异很大,但总电子能最稳定的构象都在θ=±42°附近.在任一分子、任何电子态中,离域的π体系总是失稳定的,全平面构象不是π体系最稳定的构象.无论是离域的还是定域的π体系,它们均倾向于扭曲的几何构象.π电子的离域是分子扭曲的驱动力之一.与经典观点相反,非键原子间的核排斥作用是分子扭曲的阻力,而不是动力.     

沙棘果碱提水溶多糖JS1的结构研究

沙棘（Hippophae rhamnoides L.）为胡颓子科（Elaeagnaceae）酸刺属的灌木或小乔木,它含有丰富的活性物质,具有明显的医用功效;同时已被大量用于水土保持和改善生态环境等方面,对其多糖结构的研究国内外尚未见报道。本文对沙棘果碱提水溶多糖JS1的结构进行了研究。     

沙棘果JS1多糖结构研究中GC—MS及^13C—NMR分析

近年来由于新技术的发展和应用,糖类结构的测定和生物活性的研究取得了空前的进展,大量研究表明多糖具有多方面的生物活性,如增强机体的免疫能力、抗肿瘤和抗感染等,而且多数无毒副作用。     

糖簇分子和糖树状分子及其生物学活性

糖簇分子和糖树状分子是近年来发展起来的一类新型糖缀合物,其目的是模拟天然存在的“多元效应”。本文主要综述了目前已知糖簇分子和糖树状分子所具有的生物活性及其潜在的应用领域。     

High frequency behaviours and Mossbauer study of field annealed FeCuNbSiB alloy ribbons

This paper investigates the high frequency behaviours and magnetic anisotropy of rapidly solidified FINEMET （Fe73.5Si13.sBgNb3Cul） alloy ribbons annealed in an applied magnetic field. It finds that the ribbons annealed with the applied magnetic field show much higher resonance frequencies and have even higher permeability at higher frequencies than the samples annealed without the magnetic field and the non-annealed ribbons. MSssbauer spectroscopy had been employed to study the spatial distribution of the magnetic moments of five selected FINEMET alloy ribbons in different heat-treated conditions. The results show that an easy plane has been established after annealling in the magnetic field, while for the other ribbons this effect is not significant. Hence, the relationship between magnetic field annealing and high frequency property has been bridged by the bianisotropic theory.     

Electronic structures and magnetocrystalline anisotropy energies of ordered Co1-xNix alloys: a first principles study

The electronic structures and magnetocrystalline anisotropy(MA) of ordered hexagonal close-packed(hcp) Co1-xNix alloys are studied using the full-potential linear-augmented-plane-wave(FLAPW) method with generalized gradient approximation(GGA).Great changes of magnetocrystalline anisotropy energy(MAE) are gained with different Ni compositions.Also,in-plane magnetocrystalline anisotropy is obtained for Co 15 Ni in which the Snoek’s limit is exceeded.It is found that the changes of the symmetry of the crystal field on Ni induce small variations in band structures around the Fermi level under different compositions,which plays an important role in modulating the magnetization direction,where the hybridization between Co-3d and Ni-3d orbits is of special importance in deciding the magnetocrystalline anisotropy of itinerant states.The rigid-band model is inapplicable to explain the evolution of magnetocrystalline anisotropy energy with Ni composition,and it is also inadequate to predict the magnetocrystalline anisotropy energy through the anisotropy of the orbital magnetic moment.     

CoFe2O4纳米颗粒的结构、磁性以及离子迁移

聚乙烯醇(PVA)溶胶凝胶法制备出CoFe₂O₄纳米微粉，用X射线衍射研究了铁氧体纳米颗粒的结构.测量了CoFe₂O₄纳米颗粒80—873 K的变温穆斯堡尔谱，发现纳米颗粒的磁转变温度范围为793—813 K，比块体材料的磁性转变温度要低.CoFe₂O₄纳米颗粒的德拜温度θ_A=674 K，θ_B=243 K，比块体材料要小.CoFe₂O₄纳米颗粒超精细场H_f随温度的变化符合T^3/2+T^5/2定理.当温度较高时，平均同质异能移IS随温度的升高而减小，并呈线性关系. 关键词： 纳米颗粒 磁性 穆斯堡尔谱     

Substrate Dependence of Properties of Sputtered ITO Films

High-quality indium-tin-oxide (ITO) films are deposited on p-type Czochralski silicon and 7059 Coming glass by direct-current magnetron sputtering at various temperatures. The structural, electrical and optical properties of the ITO films are investigated as functions of the substrate temperature. A comparison between the characteristics of the ITO films on silicon and Coming glass is presented. The results show that for the ITO film on silicon,the nucleation begins from room temperature; the resistivity reaches a maximum value at 75℃; the reflectivity increases with increasing temperature; when temperature is above 125℃, the ITO grows in a three-dimensional manner and forms a granular structure. However, for the ITO film on glass, it is still in an amorphous state at 75℃. Moreover, both the resistivity and the reflectivity decrease with increasing temperature. Above 125℃, the ITO grows in a two-dimensional manner and forms a domain structure.