First-Principles Study of Electronic Structure of the Laves Phase ZrFe2

We perform the ab initio calculation for obtaining the density of states and magnetic properties of ZrFe2 Laves phase compound based on the method of augmented plane waves plus local orbital The results indicate that the ferromagnetic state is more stable than the paramagnetic one, but with a slightly larger volume. The 3d - 4d exchange interactions between Fe and Zr electrons lead to the antiparallel coupling for Fe 3d and Zr 4d states, which is responsible for the ferrimagnetic ordering of the compound. The resulting magnetic moment of about 1.98μB for Fe is spatially localized near the Fe site, while around Zr a small but extended negative spin states causes a moment of about -0.44 μB. Moreover, the resulting magnetic moments with the generalized gradient approximation are more consistent with experimental values than that of the local-spin density approximation.     

Magnetic domain structures of precipitation-hardened SmCo 2：17-type sintered magnets： Heat treatment effect

The typical magnetic domains of Sm（CObalFe0.25Cuo.07Zr0.02）7.4 magnets quenched through various heattreatment steps have been revealed by using magnetic force microscopy （MFM）. For the specimens in which the nominal c-axis is perpendicular to the imaging plane, the domain configurations change from plate-like for the as-sintered magnet to corrugation and spike-like for the homogenized one, and then to a coarse and finally to a finer domain structure when isothermally aged at 830℃ and then annealed at 400℃. However, only plate-like domains can be detected on the surfaces with the nominal c-axis parallel to the imaging plane. The finer domain （so-called interaction domain） is a characteristic magnetic domain pattern of the SmCo 2：IT-type magnets with high coercivities. Domain walls in a zigzag shape are revealed by means of MFM in final bulk SraCo 2：17-type sintered magnets.     

SmCo5型中熵、高熵金属间化合物的结构与磁性

以SmCo₅为原型,设计了3种中熵金属间化合物(Sm_1/3Ce_1/3Pr_1/3)Co₅、(Sm_1/3Ce_1/3Nd_1/3)Co₅、(Sm_1/3Pr_1/3Nd_1/3)Co₅和1种高熵金属间化合物(Sm_1/4Ce_1/4Pr_1/4Nd_1/4)Co₅,并采用原子半径差和混合焓预测了形成单相结构的可能性. 应用真空电弧熔炼技术成功制备了4种金属间化合物. 采用X射线衍射仪(XRD)、能谱仪(EDS) 和振动样品磁强计(VSM) 表征了样品的物相、成分和磁学性能. 结果表明:4种化合物均为单相,具有六方CaCu₅结构,空间群为P6/mmm,稀土原子占据1a位置;稀土位置上的原子浓度为等原子比;化合物的室温磁化行为遵循Langevin模型,磁化强度依赖于化合物的成分;磁价模型计算证实了化合物(Sm_1/3Ce_1/3Pr_1/3)Co₅、(Sm_1/3Ce_1/3Nd_1/3)Co₅和(Sm_1/4Ce_1/4Pr_1/4Nd_1/4)Co₅中的Ce为+4价,对磁矩没有贡献.     

Correlation between electronic structure and energy band in Eu-doped CuInTe_2 semiconductor compound with chalcopyrite structure

The Eu-doped Cu(In, Eu)Te_2 semiconductors with chalcopyrite structures are promising materials for their applications in the absorption layer for thin-film solar cells due to their wider band-gaps and better optical properties than those of CuInTe_2. In this paper, the Eu-doped CuInTe_2(CuIn_(1-x)Eu_xTe_2, x = 0, 0.1, 0.2, 0.3) are studied systemically based on the empirical electron theory(EET). The studies cover crystal structures, bonding regularities, cohesive energies, energy levels,and valence electron structures. The theoretical values fit the experimental results very well. The physical mechanism of a broadened band-gap induced by Eu doping into CuInTe_2 is the transitions between different hybridization energy levels induced by electron hopping between s and d orbitals and the transformations from the lattice electrons to valence electrons for Cu and In ions. The research results reveal that the photovoltaic effect induces the increase of lattice electrons of In and causes the electric resistivity to decrease. The Eu doping into CuInTe_2 mainly influences the transition between different hybridization energy levels for Cu atoms, which shows that the 3d electron numbers of Cu atoms change before and after Eu doping. In single phase CuIn_(1-x)Eu_xTe_2, the number of valence electrons changes regularly with increasing Eu content,and the calculated band gap E_g also increases, which implies that the optical properties of Eu-doped CuIn_(1-x)Eu_xTe_2 are improved.     

Synthesis,structure, optical,and electric properties of Ce-doped CuInTe_2 compound

Ce-doped Cu In Te2（CICT） semiconducting compounds are successfully synthesized. The phase structures, optical,and electric properties are investigated using powder X-ray diffraction（XRD）, field emission scanning electron microscopy（FESEM）, X-ray photoelectron spectrometer（XPS）, Raman spectrometer, ultraviolet and visible spectrophotometer（UVVis）, and a standard four-probe method. Cu In1-xCex Te2 crystallizes into a tetragonal structure with predominant orientation along the [112] direction. The lattice parameters are a = 6.190（6） A–6.193（0） A and c = 12.406（5） A–12.409（5） A. Ce prefers to occupy the 4b crystal position. According to the analysis of XPS spectra, Ce shows the mixture of valences 4＋and 3＋. Raman spectra reveal that the photon vibrating model in the CICT follows A1 mode in a wavenumber range of123 cm^-1–128 cm^-1. UV-Vis spectra show that the band gap Eg values before and after 0.1 mole Ce doped into Cu In Te2 are 1.28 e V and 1.16 e V, respectively. It might be due to the mixture of valences for Ce. Ce doped into Cu In Te2 still shows the semiconductor characteristics.     

FeTe合金结构分析及其薄膜制备

利用固态反应法制备了名义成分为FeTe的合金, 采用X射线粉末衍射技术和Rietveld全谱拟合分析方法测定了其相组成和晶体结构. 研究表明,主相为Fe_1.08Te,空间群为P4/nmm,点阵参数 a = 3.8214(3) Å, c = 6.2875(3) Å, Z = 2, Fe原子占据2a和2c晶位, Te原子占据2c晶位. 利用脉冲激光沉积技术制备的FeTe薄膜超导转变起始温度为13.2 K,零电阻温度为9.8 K. 关键词： FeTe Rietveld结构精修 超导薄膜     

化合物SmCo5的电子结构、自旋和轨道磁矩及其交换作用分析

用自旋极化的MS-Xα方法研究了稀土-过渡族化合物SmCo5₅的电子态密度、自 旋能级劈裂及原子磁矩.研究结果显示，由于化合物中Sm-Co间的轨道杂化效应，使Sm原子原来的5d00空轨道上占据了少量5d电子.由于Co(3d)-Sm(5d)电子间的直接交换作用，导致了Sm-Co间的磁性交换耦合，这是化合物中形成Sm-Co铁磁性长程序的一个重要原因.在SmCo5_{5化合物中存在6个能级呈现负交换耦合，导致了SmCo55化 关键词： 电子结构 自旋极化 原子磁矩 交换耦合}     

La-Mg-Ni/Co储氢合金中的相结构

应用真空电弧熔炼方法制备La-Mg-Ni/Co5：19和2：7型储氢合金.应用X射线衍射系统研究这两类合金的相结构,并测定各相的原子占位.研究表明：5：19型的（La1-xMgx）5Co19合金是由Pr5Co19,LaCo5和LaSb3V3种类型结构组成;在2：7型的（La1-xMgx）2Ni7合金中,除了（La0.85Mg0.15）2Ni7合金只含LaNi5类型相结构外,其他合金均含有LaNi5类型相结构及LaNi3或La2Ni7类型相之一.应用尝试法确定合金中各相的晶胞参数和体积的变化规律,并利用Rietveld全谱拟合分析方法测定了（La0.95Mg0.05）2Ni7合金的相结构及相含量.研究表明：两种储氢合金相结构中主相与晶界相的点阵常数之间存在良好的共格性.Mg原子同时部分取代La和Ni原子,随着Mg含量的增加,晶胞内空隙变大.由于吸收的H原子将占据这些空位,所以空位空间的增加有助于容纳更多的H.这暗示Mg原子的占位导致的晶体畸变与储氢合金储氢能力相关,同时由于Mg原子与H原子之间强的亲和力,以及主相与晶界相之间的共格关系,可以使得H原子更容易进人合金中,并形成稳定的相结构.     

化合物SmCo7-xTix的磁性及电子结构

用自旋极化的MS-Xα方法研究了化合物SmCo_7-xTi_x的电子态密度、自旋能级劈裂及原子磁矩. 研究表明, 由于化合物中Sm-Co间的轨道杂化效应, 使Sm(5d⁰)空轨道上占据了部分5d电子. 5d-3d 电子间的直接交换作用, 构成Sm-Co间的主要耦合方式, 这是在化合物中形成长程磁有序的一个重要因素. SmCo_7-xTi_x的居里温度比金属Co明显降低, 主要是因为2e位原子与其他原子之间存在着负交换耦合作用, 从而使Co-Co之间交换劈裂平均值减少的缘故. 研究结果也表明, 掺杂原子Ti使2e位的负耦合作用减弱, Fermi面处电子间键合作用增强, 化合物的系统自由能降低, 从而有利于形成稳定的铁磁性结构. 考虑到Fermi面处4f电子的扩展特征, 以及化合物中轨道杂化效应所产生的部分5d电子, 可以得到化合物总磁矩为9.47 μ_B, 与实验值基本符合.     

一些A_2，B_2型结构电子化合物的价电子结构分析及相变点计算

本文应用经验电子理论对一些具有Ａ＿２，Ｂ＿２型结构的电子化合物进行了价电子结构分析及相变点计算。指出了Ｈｕｍｅ－Ｒｏｔｌｉｅｒｙ和Ｐａｕｌｉｎｇ在合金元素价数问题上的矛盾所在，并分析了电子化合物相的稳定性因素．