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Exchange-coupling interaction, effective anisotropy and magnetic property of nano-magnetic materials

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Progress in Natural Science:Materials International 2007年第2期17卷 131-137页

作者： SUN Yan, GAO Ruwei, HAN Baiping, LIU Min, HAN Guangbing and FENG Weicun (school of physics and microelectronics, shandong university, jinan 250100, china) school of physics and microelectronics Shandong University Jinan 250100 China

The theories and models of exchange-coupling interaction between grains in nanocrystalline magnetic materials are introduced here. Their insufficiencies and distinctions from the experimental results are pointed out, and some revisions are made. The effects of the phase component ratio, the grain size and microstructure on the effective anisotropy and magnetic properties in the nanocomposite permanent materials and the improved models are discussed in detail.

关键词： nano-magnetic materials exchange-coupling interaction microstructure effective anisotropy magnetic property.

Influence of solidification rate on the microstructure of (Nd,Dy)_(12.8)(Fe,Co)_(80.7)B_(6.5) cast strips

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Rare Metals 2005年第2期24卷 200-204页

作者： LIUHanqiang WANGBiao HANGuangbing GAORuwei schoolofphysicsandmicroelectronics ShandongUniversityJinan250100China

The influence of solidification rate on the microstructure of (Nd,Dy)(12.8)(Fe,Co)(80.7)B-6.5 cast strips was reported in this paper. The strips prepared at different wheel speeds were analyzed by X-ray diffraction (XRD). The microstructure of the strips was investigated by backscattered scanning microscope (BSM). The XRD results show that the strips are mainly composed of the main phase (T-1) existing apparent alignment along [00L]. The thickness of T-1 columnar grains is larger when the solidification rate is lower and the over-small isotropic microcrystalline appear on the cooling surface of the strips when the solidification rate is too high. The adequate wheel speed for obtaining the optimum microstructure of the strips is about V = 2.0 m/s. The strip prepared at V = 2.0 m/s possesses suitable thickness and the highest alignment degree of T-1 columnar grains, uniformly distributed Nd-rich phase, and no existence of alpha-Fe phase. This kind of cast strip is an ideal starting material for preparing sintered magnets with high magnetic properties.

关键词： metal material microstructure solidification rate cast strip Nd-Fe-B

Ground state and polaron and bipolaron excited states in polydiacetylene

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Science china(physics,Mechanics & Astronomy) 2006年第4期49卷 430-439页

作者： LI Yuan1, HU Guichao1, XIA Caijuan1, LIU Desheng1,2 & XIE Shijie1,2 1. school of physics and microelectronics, shandong university, jinan 250100, china 2. National Key Laboratory of Crystal Materials, shandong university, jinan 250100, china school of physics and microelectronics Shandong University Jinan China National Key Laboratory of Crystal Materials Shandong University Jinan China

The electronic properties of ground state and charged excited states of nondegenerate polydiacetylene were investigated by means of a tight-binding model. The parameters of the model were obtained by comparison of the experimental and other theoretical results. It was found that there is a stable dimerized structure of polydiacetylene in ground state and the doping induces the nonlinear excitations, such as polarons and bipolarons. In order to compare the stability of polaron and bipolaron, the creation energy and binding energy were separately defined. By neglecting the electron-electron Coulomb interaction, a bipolaron is more stable than two independent polarons.

关键词： dimerization, polaron, bipolaron, binding energy.

Synthesis and structural characterization of Zn_3N_2 powder

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Science china(physics,Mechanics & Astronomy) 2005年第2期48卷 201-210页

作者： ZONG Fujian1, MA Honglei1, XUE Chengshan2, ZHUANG Huizhao2, ZHANG Xijian1, MA Jin1, JI Feng1 & XIAO Hongdi1 1. school of physics and microelectronics, shandong university, jinan 250100, china 2. Institute of Semiconductor, shandong Normal university, jinan 250014, china school of physics and microelectronics Shandong University Jinan 250100 China Institute of Semiconductor Shandong Normal University Jinan 250014 China

Zinc nitride (Zn3N2) powder has been synthesized through the nitridation reaction of Zn powder with NH3 gas (at the flow rate of 500 ml/min) at the nitridation temperature of 600℃ for 120 min. X-ray diffraction (XRD) indicates that Zn3N2 is cubic in structure with the lattice constant being a = 0.9788 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that Zn3N2 powder has surface morphology of various types. X-ray photoelectron spectroscopy (XPS) shows the differences in chemical bonding states between Zn3N2 and ZnO, and confirms the formation of N–Zn bonds. Observation through high resolution transmission electron microscopy (HRTEM) also indicates that the computer simulation of the structure of Zn3N2 is consistent with the structural model put forward by Partin.

关键词： nitridation, Zn3N2 powder, structure, XRD, SEM, TEM, HRTEM, XPS.

Electronic structure and magnetic properties of SmCo7-xTix

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Science china(physics,Mechanics & Astronomy) 2006年第1期49卷 38-45页

作者： ZHANG Changwen1, LI Hua1, DONG Jianmin1, GUO Yongquan2 & LI Wei2 1. school of physics and microelectronics, shandong university, jinan 250100, china 2. Institute of Functional Materials, Central Iron and Steel Research Institute, Beijing 100081, china school of physics and microelectronics Shandong University Jinan China Institute of Functional Materials Central Iron and Steel Research Institute Beijing China

Electronic structure of SmCo7-xTix alloy has been studied by means of the spin-polarized MS-Xα method. It is shown that a few of electrons are transferred to Sm(5d) orbital due to orbital hybridization between Sm and Co atoms. The exchange interaction between 5d-3d electrons is stronger, which is the main reason resulting in the long-range ferromagnetic order between Co and Sm atoms. The Curie temperature of SmCo7-xTix is generally lower than that of pure Co metal, which may be explained by the weaker aver- age of coupling strength between Co sites due to some negative exchange couplings occurring mainly at 2e site. The calculated results for the Sm5Co28Ti6 cluster may lead to a better understanding of why SmCo7-xTix is stable phase. Since the negative interaction of 2e sites weakens and the bonding at EF strengthens with increasing Ti concentration, which result in the decrease in the free energy of the alloy, the stable ferromagnetic order forms inside SmCo7-xTix. Considering the localization of 4f states and 5d moment arising from the orbital hybridization, the calculated moment is 9.47μB per formula unit that is in agreement with experiments.

关键词： electronic structure, spin polarization, atomic magnetic moment, exchange coupling, Curie temperature.

新型超导材料MgCNi_3的电子结构与超导电性研究

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物理学报 2004年第3期53卷 922-926页

作者：陈丽李华山东大学物理与微电子学院

用MS Xα方法研究了非氧化物超导材料MgCNi3的电子结构 .研究结果显示 ,态密度分布曲线的主峰靠近Fermi面 ,主要来自于Ni的d电子的贡献 .用T(T =Co ,Mn ,Cu)替代MgCNi3中的部分Ni形成化合物MgCNi2 T ,替代使Ni的价电子数减小 ,价态发生... 详细信息

用MS Xα方法研究了非氧化物超导材料MgCNi3的电子结构 .研究结果显示 ,态密度分布曲线的主峰靠近Fermi面 ,主要来自于Ni的d电子的贡献 .用T(T =Co ,Mn ,Cu)替代MgCNi3中的部分Ni形成化合物MgCNi2 T ,替代使Ni的价电子数减小 ,价态发生变化 ,Fermi面处态密度N(EF)减小 .计算结果表明 :无论是电子掺杂 (Cu)还是空穴掺杂 (Co ,Mn) ,MgCNi3的超导电性都被抑制 ;Mn掺杂比Co掺杂更快地抑制超导电性。

关键词：超导材料电子结构态密度超导电性镍碳镁材料 Fermi面电子掺杂空穴掺杂

Electronic structure and magnetic properties of metastable SmCo_(7) compound

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Science china(physics,Mechanics & Astronomy) 2005年第3期48卷 325-335页

作者： ZHANG Changwen 1 , LI Hua 1 , DONG Jianmin 1 , WANG Yongjuan 1 , PAN Fengchun 1 , ZHANG Jian 1 , GUO Yongquan 2 & LI Wei 2 1. school of physics and microelectronics, shandong university, jinan 250100, china 2. Institute of Functional Materials, Central Iron and Steel Research Institute, Beijing 100081, china school of physics and microelectronics Shandong University Jinan China Institute of Functional Materials Central Iron and Steel Research Institutes Beijing China

The electronic density of states, spin-splittings and atomic magnetic moments of SmCo 7 compound have been studied using spin-polarized MS-Xα method. The results show that a few of electrons are transferred to Sm(5d 0 ) orbital because of orbital hybridization between Sm and Co atoms in the compound. The exchange interactions between 3d and 5d electrons lead to the magnetic coupling between Sm and Co, and therefore, result in the long-range ferromagnetic order inside the SmCo 7 compound. There are negative exchange couplings occurring at some levels, which weakens the strength of average coupling around Co lattice. So, the Curie temperature and Co-moment of SmCo 7 decrease distinctly compared with pure Co. Compared with SmCo 5 compound, the disordered substitution of Co-Co “dumbbell-atom” pairs for Sm changes the local environment of Co lattice, which makes the 2e site bear negative magnetic moment. The strength of hybridization near Fermi level weakens and the free energy of the compound increases obviously. Thus, SmCo 7 is a metastable compound at room temperature. Considering the localization of 4f electrons and a few of 5d electrons arising from the orbital hybridization, the magnetic moment of Sm atom will be 1.61μ B in SmCo 7 compound, which is in agreement with the experimental values of Sm 3+ ion- moment and Sm atom-moment in metals.

关键词： electronic structure, spin polarization, atomic magnetic moment, exchange coupling, Curie temperature.

Theoretical study on optical and electronic properties of phthalocyanine and phthalocyanine-ferrocene complexes

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Theoretical study on optical and electronic properties of ph...

低温磁控溅射SnO_2:Sb透明导电膜的结构与导电性能

中国化学会第九届全国量子化学学术会议

作者： Zhou Yufang, Cui Bin school of physics and microelectronics, shandong university, jinan 250100, china

＜正＞Organometallics have an area of interesting research for recent years, due to their applicability in a variety of fields, such as liquid crystals, semiconductor, nonlinear optics and electron transfer etc [1]. Organimetallic compounds have two types of charge-transfer transitions, i.e., metal-to-ligand and ligand-to-metal. The metal-ligand bonding displays large molecular hyperpolarizability duo to the transfer of electron density between the metal atom and the conjugated ligand systems.

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来源： cnki会议评论

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太阳能学报 2004年第2期25卷 148-151页

作者：马瑾刘晓梅张士勇郝晓涛马洪磊山东大学物理与微电子学院光电材料与器件研究所济南250100 山东大学计算机学院济南250100 长安大学基础部物理组西安710064

采用射频磁控溅射法在7059玻璃衬底上低温制备出锑掺杂的氧化锡(SnO2:Sb)透明导电膜,对薄膜的结构和电学性质进行了研究。制备薄膜为多晶膜,并且保持了纯二氧化锡的金红石结构,而且具有明显的(110)择优取向。最低电阻率为2×10-3Ω·cm... 详细信息

采用射频磁控溅射法在7059玻璃衬底上低温制备出锑掺杂的氧化锡(SnO2:Sb)透明导电膜,对薄膜的结构和电学性质进行了研究。制备薄膜为多晶膜,并且保持了纯二氧化锡的金红石结构,而且具有明显的(110)择优取向。最低电阻率为2×10-3Ω·cm,载流子浓度和迁移率分别为1 65×1020cm-3和19 0cm2·v-1·s-1。

关键词：磁控溅射 SnO2:Sb薄膜结构和电学性质