1991年国际磁学会议(ICM’91)

ICM’91于 91年 9月 2日到 6日,由英国物理学会受IUPAP委托具体主办,在英国爱丁堡市召开.出席大会的学者超过1200人,来自35个国家.一些国际著名磁学专家,如R. Elliot(牛津大学),A.J.Free-man(西北大学);R·M·White(斯坦福大学),T.Moriya(东京科技大学),S.V.Vonsovskii(苏联)等教授出席了会议.日本这次派了近250人名学者参加会议,是代表人数最多的国家,其次是英国、法国、德国和美国.波兰和原苏联的代表人数超过50名.我国派出代表七名,还有九名在国外的学者也出席了会议. 会议交流的论文总数为1469篇,日本为281抿,占18呢,其次为法…     

Nb掺杂对还原性烧结的TiO2-δ陶瓷的晶体结构及热电性能的影响

利用传统的固相反应法在还原性气氛1200 ℃下分别制备出不同Nb掺杂量的Ti_1-xNb_xO_2-δ陶瓷样品.样品的粉末X射线衍射(XRD)结果显示:Nb掺杂量x较低时样品为多相混合,当Nb掺杂量x>0.02时样品为单一的四方相金红石型结构.在室温到900 K的测试温区,测试了单相样品(x=0.02,0.03,0.04)的电导率、Seebeck系数和热导率.测试 关键词： 氧化钛陶瓷 热电性能 氧空位     

掺杂聚乙炔中的边界效应与孤子对稳定性

在自然边界条件下,研究了含有两个杂质离子的反式聚乙炔链中孤子对的稳定性和电子能级结构。所用哈密顿量在SSH模型基础上,附加了一个端点势,并包含了杂质的屏蔽库仑势及格点上e-e相互作用。计算结果显示,杂质离子的库仑作用力程足够长时,链中形成稳定的孤子对,链端的影响增强这种稳定性。带隙宽度随链的增长而变窄,但孤子能级至导带底的跃迁能量随链长变化不明显。 关键词：     

四原子分子的转动-振动能级的李代数处理-Ⅰ线性X_2Y_2型分子

本大利用李代数方法与二次量子化理论计算了四原子分子的转动—振动能级.结果表明,如果将分子的转动与振动均看作是谐振子,则可以导出线性X_2V_2型分子的转动—振动能级公式。     

Variations from Zn1-xCoxO Magnetic Semiconductor to Co-ZnCoO Granular Composite

We investigate the variations from as-deposited Zn1-x： Cox O magnetic semiconductors to the post-annealed Co- ZnCoO granular composite. The as-deposited Zn1-x Cox 0 magnetic semiconductor deposited under thermal nonequilibrium conditions is composed of Zn1-x. Cox O nanograins of high Co concentration. The room-temperature ferromagnetism with high magnetization and large negative magnetoresistance are found in the as-deposited samples. By annealing, the samples become of granular composite consisting of the Co metal grains and the remanent Zn1-x CoxO matrix. Although the magnetization is enhanced after annealing, the spin-dependent negative magnetoresistance disappears at room temperature. The magnetoresistance observed in the annealed samples in the high field region has no relation with the ferromagnetism, which in turn indicates that the roomtemperature ferromagnetism and large negative magnetoresistance observed in the as-deposited are the intrinsic properties of the Zn1-x Cox O magnetic semiconductor.     

金属光子晶体禁带研究

通过数值方法计算了铜(Cu),银(Ag)，金(Au)，铝(Al)四种金属构成的光子晶体的禁带，给出了禁带与金属填充率f的关系曲线,对比了几种金属光子晶体禁带的差异.计算针对TM模的情况，取光子晶体的晶格常量a=0.775 μm.     

Epitaxial Properties of Co-Doped ZnO Thin Films Grown by Plasma Assisted Molecular Beam Epitaxy

High quality Co-doped ZnO thin films are grown on single crystalline Al2O3（0001） and ZnO（0001） substrates by oxygen plasma assisted molecular beam epitaxy at a relatively lower substrate temperature of 450℃. The epitaxial conditions are examined with in-situ reflection high energy electron diffraction （RHEED） and ex-situ high resolution x-ray diffraction （HRXRD）. The epitaxial thin films are single crystal at film thickness smaller than 500nm and nominal concentration of Co dopant up to 20%. It is indicated that the Co cation is incorporated into the ZnO matrix as Co^2＋ substituting Zn^2＋ ions. Atomic force microscopy shows smooth surfaces with rms roughness of 1.9 nm. Room-temperature magnetization measurements reveal that the Co-doped ZnO thin films are ferromagnetic with Curie temperatures Tc above room temperature.     

一维导电聚合物中的电子关联(Ⅰ)——中性孤子

本文仔细地研究准一维电子-晶格系统中的电子关联,提出一种“超平均”电子-电子相互作用,通过考虑近邻的电子相互作用on-site,site-site,site-bond,以及on-bond等四项,建立一个相互作用模型哈密顿量,数值计算结果很好地解释反式聚乙炔中的中性孤子的光谱实验和ENDOR实验结果。 关键词：     

La0.5Ba0.5CoO3中Y的替代效应

用固相反应法制备了La0.5Ba0.5CoO3多晶材料，系统研究了Y的替代对材料磁性和输运特性的影响，结果发现，Y的掺入主要产生了两种效应，一是Y向Co的3d轨道产生了电荷转移，使分子磁矩下降，二是出现了Co离子的反铁磁交换作用，当Y含量少于或等于0.3时，材料中出现了自旋的非共线结构。当Y含量大于0.3时，材料从铁磁态为主转变为反铁磁态为主，对不同Y含量的材料，其导电机制都属于极化子的变程跳跃导电，随Y含量增加，材料电经迅速增大。     

Ferromagnetism, variable range hopping and anomalous Hall effect in epitaxial Co:ZnO thin film

A series of high quality single crystalline epitaxial Zn_0.95Co_0.05O thin films is prepared by molecular beam epitaxy. Superparamagnetism and ferromagnetism are observed when the donor density is manipulated in a range of 10¹⁸ cm^-3-10²⁰ cm^-3 by changing the oxygen partial pressure during film growth. The conduction shows variable range hopping at low temperature and thermal activation conduction at high temperature. The ferromagnetism can be maintained up to room temperature. However, the anomalous Hall effect is observed only at low temperature and disappears above 160 K. This phenomenon can be attributed to the local ferromagnetism and the decreased optimal hopping distance at high temperatures.