稀土元素在光、电、磁方面的研究应用进展

综述了稀土元素在光、电、磁方面的应用，并对其应用进展情况作了分析和研究，指出稀土元素及其化合物表现出了许多独特的光、电、磁学性质，使得它在工、农业生产，现代高科技研究及国防现代化建设中有着十分广泛的应用前景．近年来，国内外开展了广泛的研究开发工作，特别是在新型功能材料方面，并取得了一系列的重要成果．     

物理、力学和天文中的手征性专题·编者按

1848年,不到26岁的法国学者、巴氏消毒法的发明人巴斯德利用显微镜,发现葡萄酒沉淀中存在两类晶体,它们的结构呈镜像对称.两类晶体的溶液能够使偏振光的偏振方向分别沿顺时针旋转和逆时针旋转.分子结构的手性从此进入了人们的视野.就跟左手和右手一样,不同手征性(简称手性)的同一种分子其结构呈现镜像对称,且两者不可重合.     

The electronic structures, magnetism and metastable states of DNA

Molecular devices are the ultimate goal in the miniaturization of the electronic technology. Based on the unique properties of DNA (e.g. self-assembly and molecular recognition), people have made great efforts to develop molecular devices in the last few …     

Mars' core and magnetism.

The detection of strongly magnetized ancient crust on Mars is one of the most surprising outcomes of recent Mars exploration, and provides important insight about the history and nature of the martian core. The iron-rich core probably formed during the hot accretion of Mars approximately 4.5 billion years ago and subsequently cooled at a rate dictated by the overlying mantle. A core dynamo operated much like Earth's current dynamo, but was probably limited in duration to several hundred million years. The early demise of the dynamo could have arisen through a change in the cooling rate of the mantle, or even a switch in convective style that led to mantle heating. Presently, Mars probably has a liquid, conductive outer core and might have a solid inner core like Earth.     

浓磁半导体材料的制备、磁性和自旋极化的输运

成功制备出过渡金属元素含量高的Zn_1-xCo_xO、Ti_1-xCo_xO₂、(In_1-xCo_x)2O3铁磁半导体(浓磁半导),发现这些氧化物浓磁半导体具有高于室温的居里温度、高自旋极化率、巨磁光克尔效应等优良材料特性。还对浓磁半导的输运性质进行了系统的实验和理论研究,提出了自旋依赖的电子变程跃迁理论模型。这些用新方法制备的氧化物浓磁半导体,不同于常规的稀磁半导体,有望成为高效自旋注入源和半透明磁光新材料。     

Biomineralization and magnetism of bacterial magnetosomes

Magnetosomes of magnetotactic bacteria are of great interest in understanding biomiueralizatiou and possible links between organisms and geomagnetic field. Fossil maguetosomes are ubiquitous in marine and lake sediments and may significantly contribute to magnetic signals. In this review, we firstly introduce some characteristics of magnetotactic bacteria, followed by considering recent progress in maguetosome formation, magnetic measurements, and identification of bacterial magnetites in bulk sediments as well as their paleoenviroumeutal implications. Finally, we briefly discuss potential future breakthroughs in magnetosome studies and its applications.     

Fe掺杂TiO2结构和磁性

在退火温度为773K、Fe掺杂量为n(Fe)/n(Fe+Ti)=1∶25的制备条件下,用溶胶-凝胶法在空气氛围中制备Fe掺杂TiO2稀磁半导体纳米粉末;用直流磁控溅射方法并在真空和空气氛围中结合原位退火工艺,在普通玻璃基片上制备Fe掺杂TiO2薄膜.利用X射线衍射仪(XRD)对其结构进行表征,振动样品磁强计(VSM)对磁性进行表征.结果表明,溶胶-凝胶法制备的粉末材料的磁性为室温顺磁性;直流磁控溅射法制备的薄膜样品在空气和真空氛围中均为室温铁磁性,其中真空退火能够产生更强的铁磁性.这说明可能是薄膜和基底的相互作用产生和铁磁性至关重要的氧空位,而真空环境退火能够增加氧空位.     

生物分子的手性与观控相对论

本分析了生物分子手性的起源，提出了一种新的看法，即非平衡态可诱导产生手性（在分支点的对称破缺），而非对称性又造成了新的非平衡态，生命就是在这种非平衡态中延续发展的，生命的结构物质，在不对称中，在时间箭头的方向上不可逆地产生着，发展着，演化着，这一演化过程是一个结构和功能不断调整，不断适应的观控相对统一体。     

生物多聚体分子手性的起源

本文提出了手性分子聚合的合作理论，给出了各种手性参量的关系．证明生物前进化存在两种基本模式：一是大手性能量和小立体选择性的模式，其手性只能通过化学反应镜对称的自发破缺产生；二是小手性能量和大立体选择性的模式，其手性可通过弱作用产生     

电与磁在教学中的对称性

在大学物理教学中，相关对称性的教学内容很多，但电与磁间的对称性更为广泛，掌握其内在联系的对称性，对提高教学效率更有意义。     

碳纳米管的手性对发射电流的影响

建立了SWCNT的发射电流与外加电场之间的关系式，分析了SWCNT的手性结构对发射特性的影响．数值计算的结果表明，在电场相同、管径相近的情况下，发射电流从大到小依次为锯齿型(金属性)、扶手椅型、手性(金属性)、手性(半导体性)和锯齿型(半导体性)管．     

First-principles studies for magnetism in Cu-doped GaN

Hole carrier mediated magnetization in Cu-doped GaN is investigated by using the first-principles calculations.By studying the sp-d interaction and the direct exchange interaction among the dopants,we obtain an equation to determine the spontaneous magnetization as a function of the Cu dopant concentration and the hole carrier density.It is demonstrated that nonmagnetic Cu doped GaN can be of room-temperature ferromagnetism.The system’s Curie temperature Tc can reach about 345 K with Cu concentration of 1.0% and hole carrier density of 5.0×1019 cm-3.The results are in good agreement with experimental observations and indicate that ferromagnetism in this systems is tunable by controlling the Cu concentration and the hole carrier density.     

Ca1-xYxMnO3体系的电磁输运性能及团簇玻璃态行为

文章系统地研究了电子型掺杂Ca1-xYxMnO3(0＜x≤0.3)体系的电阻、磁化强度与温度的关系.结果表明,当x≤0.10时,Ca1-xYxMnO3的电阻率随着钇掺杂量的增加而减小,同时反铁磁性(AFM)减小,铁磁性增强;当0.15≤x≤0.30时,Ca1-xYxMnO3电阻率随着钇掺杂量的增加而增加,反铁磁性逐渐增强,铁磁性减弱;另外,磁化强度测量观察到Ca1-xYxMnO3低温下的团簇玻璃态行为,其原因是随着钇离子掺杂量的升高,样品中的Mn3+离子增加并且Mn3+和Mn4+离子不均匀分布导致反铁磁和铁磁团簇在低温下随机共存.