三核苯甲酸铁配合物[Fe3O(OBZ)6(H2O)3](NO3)(acetone)5(OBZ-=苯甲酸根)的结构和磁性

合成了三核苯甲酸铁配合物［Ｆｅ３Ｏ（ＯＢＺ）６（Ｈ２Ｏ）３］（ＮＯ３）（ａｃｅｔｏｎｅ）５。测定了其晶体结构，其中三个铁形成等边三角形结构。配合物的变温磁化率表明，分子内三个铁之间有弱的反应磁性交换作用，Ｊ＝－３３．１８ｃｍ＾－１。分子之间则有更弱的反铁磁性交换作用，ＺＪ＾＇＝－１．１４ｃｍ＾－１。     

Perturbation expansions for quantum many-body systems

A systematic method for developing high-order, zero-temperature perturbation expansions for quantum many-body systems is presented. The models discussed explicitly are spin models with a variety of interactions, in one and two dimensions. The wide applicability of the method is illustrated by expansions around Hamiltonians with ordered and disordered ground states, namely Ising and dimerized models. Computer implementation of this method is discussed in great detail. Some previously unpublished series are tabulated.     

SrRuO3的电子结构与磁性研究

用自洽的全势能线性丸盒轨道能带方法计算了氧化物体系SrRuO₃(SRO)的电子结构和磁性.对于理想的立方钙钛矿结构的计算得出的电子结构明显改善了已有的计算结果:每个元胞的磁矩为129μ_B,按原子球划分为084μ_B/Ru原子和011μ_B/O原子;Sr原子上的自旋磁矩几乎为零;费米能级处的态密度N(E_F)为435(states/Ryd/f.u.).关于实际的正交结构SRO,计算得出磁矩为108μ关键词： 过渡金属氧化物 电子结构 磁性     

Fe、Co、Ni混合团簇磁性的密度泛函研究

基于13原子二十面体结构,采用密度泛函方法系统计算研究了Fe、Co及Ni单质及二元混合团簇的磁性.发现有限温度下团簇磁性随结构畸变的敏感性随Fe、Co、Ni顺序逐渐减弱,同时发现二十面体结构Fe_(13)及Co_(13)均具有不同磁矩的近简并低能态.对FeNi及CoNi混合团簇、其磁矩随组分的变化不存在反常现象,但对于FeCo混合团簇、其磁矩随组分的演化行为存在个别反常现象.我们认为:这种反常现象能够对FeCo非晶合金中的实验观测结果提供一种可能的理论解释.     

Electronic structure and magnetic properties of rare-earth perovskite gallates from first principles

The density functional calculation is performed for centrosymmetric(La–Pm) GaO_3 rare earth gallates, using a full potential linear augmented plane wave method with the LSDA and LSDA+U exchange correlation to treat highly correlated electrons due to the very localized 4f orbitals of rare earth elements, and explore the influence of U = 0.478 Ry on the magnetic phase stability and the densities of states. LSDA+U calculation shows that the ferromagnetic(FM) state of RGaO_3 is energetically more favorable than the anti-ferromagnetic(AFM) one, except for LaGaO_3 where the NM state is the lowest in energy. The energy band gaps of RGaO_3 are found to be in the range of 3.8–4.0 eV, indicating the semiconductor character with a large gap.     

二维磁性纳米材料的可控合成及磁性调控

自旋电子学的研究重点在于同时利用电子的电荷和自旋两个自由度对信息进行处理和存储,其具有运行速度快、存储密度高和能耗低等优势。毫无疑问,发展二维磁性纳米材料的可控合成方法及磁性调控策略,对于新型自旋电子学器件的构筑具有重要的科学意义和应用价值。然而,目前得到的二维磁性纳米材料的种类十分有限,而且合成方法及磁性调控手段相对单一,极大地限制了该领域的发展。本文首先根据磁性的来源,对二维磁性纳米材料进行了分类,介绍了诱导产生的磁性和具有本征磁性的二维纳米材料,然后详细地归纳了二维磁性纳米材料常见的合成方法,如机械剥离法、电化学剥离法、化学气相沉积法以及液相合成方法等。此外,着重总结了二维材料磁性的主要调控手段,最后展望了该领域遇到的瓶颈、未来的研究重点及应用前景。     

稀土永磁薄膜材料

简要地介绍在纳米复合稀土永磁薄膜材料、各向异性稀土永磁薄膜材料方面的进展。在纳米复合稀土永磁薄膜材料中实现磁性交换耦合和剩磁增强效应，系统地研究了其结构与磁性的关系。制备成功高磁能积的各向异性稀土永磁薄膜材料，比较了Ti或Mo缓冲层对Nd-Fe-B薄膜的表面形貌、磁畴结构和磁性能的影响。发现薄膜的表面形貌强烈地依赖于缓冲层的厚度。由于它极大地影响薄膜的成分，溅射速率被证明是控制薄膜的显微结构、表面形貌和磁性能的一个重要因素。在微磁学模型的基础上，通过分析从5到300K的矫顽力温度依赖关系。研究了各向异性Pr-Fe-B薄膜的矫顽力机制。在晶粒表面，由于磁各向异性的降低和局域退磁场的提高导致的反转畴的形核被确定为控制各向异性Pr-Fe—B薄膜的磁化反转过程的首要机制。     

Solid-state photochemical generation of polymeric polyradicals: Poly(4-vinylphenoxy) and copolymers with styrene

Synthesis of poly(4′-vinyl-2,4,6-tri-tert-butyl-diphenyloxalate) and its 65 : 35 and 19 : 81 copolymers with styrene are described. Rigid phase broad-band photolysis of the homopolymer with a quartz filtered xenon arc at 77 K results in production of up to 25% of the theoretical number of spins/mol expected for quantitative production of pendant phenoxyl radicals, and shows no major loss of radical signal in the ESR at temperatures below 100 K. Curie law analysis of the temperature dependence of the ESR radical signal intensity for the neat photolyzed homopolymer 1 shows curvature consistent with antiferromagnetic pairing of radical spins at low temperatures. Since through-bond conjugation of radical spins is not possible in this system, the antiferromagnetic interaction is interpreted in terms of intrachain and/or interchain through-space exchange interactions.