镍-二硫代乙烯类配合物Rn[Ni(bbdt)2]的电磁学性能研究

在合成Rn[Ni(bbdt)2]系列配合物的基础上,通过EPR谱、XPS谱、变温磁化率和室温电导率的测定。研究了配合物的电磁学性能．结果表明,在Rn[Ni(bbdt)2](n=0,0．5,1,2)系列配合物中,n=0,0．5,1对应的配合物室温EPR谱中有特征的单电子信号;XPS测定的结合能数据说明,中心Ni离子对阴离子部分的荷电量不敏感。而配体S原子的结合能随荷电量有较大变化;n=0,0．5对应的配合物表现出较好的电磁学性能。     

关于钴基单分子磁体的研究进展

单分子磁体是涉及合成化学、材料科学和凝聚态物理等边缘学科的一个新颖课题。设计和合成具有特定结构和物理功能单分子磁体是近年来化学研究的一个热门方向。由于二价钴离子具有高达三个未成对电子,并且具有很大的单离子各项异性行为,因而成为构筑单分子磁体的一类重要金属离子。本文主要介绍了钴基单分子磁体的结构、制备方法、磁性、直流和交流磁化率、低温时不同振荡频率下的磁滞回线等几个方面,并对其发展前景进行了展望。     

化合物[(NiCp_2)_2H_n]XW_(12)O_(40)·xTHF(X=Si,P,Ge)的合成,表征及磁性质研究(英文)

报道了化合物［（NiCp_2）_2H_n］XW_(12)O_(10)·2THF,（CP2Ni）2HPW12O40·3THF,（CP2Ni）2H2GeW12O40·3THF的合成,表征,顺磁共振及变温磁化字研究结果表明二茂镍在化合物中为一价阳离子且它们之间在77～300K之间无明显孩交换作用．红外的紫外可见光浴表明二茂馊阳离子与多酸阴离子之间存在弱的相互作用．     

Superconductivity in the non-oxide perovskite MgCNi3

The interplay of magnetic interactions, the dimensionality of the crystal structure and electronic correlations in producing superconductivity is one of the dominant themes in the study of the electronic properties of complex materials. Although magnetic interactions and two-dimensional structures were long thought to be detrimental to the formation of a superconducting state, they are actually common features of both the high transition-temperature (Tc) copper oxides and low-Tc material Sr2RuO4, where they appear to be essential contributors to the exotic electronic states of these materials. Here we report that the perovskite-structured compound MgCNi3 is superconducting with a critical temperature of 8 K. This material is the three-dimensional analogue of the LnNi2B2C family of superconductors, which have critical temperatures up to 16 K (ref. 2). The itinerant electrons in both families of materials arise from the partial filling of the nickel d-states, which generally leads to ferromagnetism as is the case in metallic Ni. The high relative proportion of Ni in MgCNi3 suggests that magnetic interactions are important, and the lower Tc of this three-dimensional compound-when compared to the LnNi2B2C family-contrasts with conventional ideas regarding the origins of superconductivity.     

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。     

Nd-Fe-B磁体热等静压烧结的实验研究

研究了热等静压烧结对Nd-Fe-B磁体的致密度、显微组织及磁性能的影响.结果表明:与常压烧结磁体相比,热等静压烧结磁体的内部存在较多的孔洞,致密度、晶粒取向度及磁性都有所降低.用加热Ar气热膨胀而产生热等静压进行烧结的办法不适于制造高性能的烧结磁体.     

镍超细微颗粒的核磁共振研究

报导了对镍超细微颗粒进行核磁共振研究的初步结果通过测量６１Ｎｉ的零场核磁共振谱研究镍超细微颗粒的赵精细磁场的分布．微颗粒平均直径约２０ｎｍ．为了对比，还对镍粉（粒径约７６μｍ）进行了类似测量．发现微颗粒与块状样品的核磁共振谱的共振峰位置基本相同，但在线型、谱宽和信噪比方面明显不同。这表明其超精细磁场的分布有特征性的区别．镍超细微颗粒的共振谱比块状样品稍微展宽．因为超细微颗粒的表面原子数目比块状样品的多，谱线变宽可能与超细微颗粒的表面效应有关。     

分子基磁性材料的发展和展望

概述了近年来分子基磁性材料研究中的一些相关问题,介绍了分子磁体的种类和功能,并对其研究和发展历史进行了回顾。在简明阐述当前分子基磁性材料研究中一些典型的单分子磁体的研究和发展趋势的基础上,对分子磁性材料研究中的热点问题进行了介绍,并展望了分子基磁性材料研究前景。     

Syntheses, crystal structure and magnetic properties of Rm+nCo5m+3nB2n

The phase relations at the 600℃ and 700℃ isothermal sections of the ternary systems R-Co-B for R= Nd, Pr and R = Sm, Gd respectively were summarized in this paper. For Rm+ n Co5m+3n B2n, two new types ofcompounds R3Co13B2(R=Pr, Nd, Sm, Gd, Dy, Ho, Er, Y) (m=2, n=1) andR5Co19B6(R=Pr, Nd) (m=2,n = 3 ) were synthesized by utilizing the principle of structural combination. Their crystalstructures and easymagnetization direction were determined by X-ray powder diffraction, and structures were refined by the Rietveldmethod. The Curie temperature Tc, saturation magnetization M8 and anisotropic field HA of the new compounds weremeasured using a vibrating-sample magnetometer, an extraction sample magnetometer and M(H) - H curves of samplesin different magnetization directions respectively. The Tc and Ms of Rm + n Co5 m + 3 n B2n increase with increasing values of mat a given n value. HA increases with an increase in n when m is kept invariable. The effects of the substitution of Ni for Co on the magnetic properties of Nd13 Co15- x Nix B2 were also investigated. It was found that TsR decreased monotonously as the concentration of Ni increased, and at x = 3 the easy magnetization direction becomes axial at room temperature. The relations between crystal structure and magnetic properties of Rm + nCo5m+ 3nB2n and the possible routes of synthesizing permanent magnetic materials are also discussed.     

氧对Sm(Co,Fe,Cu,Zr)z永磁体性能和显微组织的影响

研究了氧对Sm(Co, Fe, Cu, Zr)z永磁体性能的影响,并借助SEM、EDS和TEM等方法分析了永磁体的显微组织变化,讨论了影响磁体性能的原因.结果表明:在氧含量不高时(质量分数＜0.32%)对磁性能的影响不明显,永磁体具有良好的磁性能;在0.32%～0.4%时,随氧含量的增加磁性能开始下降;氧含量大于0.4%后,磁性能急剧恶化;当大于0.7%后,磁性能基本消失.随着氧含量的增加,磁体的晶粒尺寸减小,以Sm2O3为主的白色析出物增多.非磁性相的增多和有效Sm含量的减少是影响磁性能的主要原因.     

Progress in magnetic couple system of nitroxidemetal complexes

Metal_radical method is an effective approach to synthesizing magnetic molecular materials. With the development in decades, the study of nitroxide_metal complexes has made great progress in model, theoretical treatment and design of molecules. Several mechanisms of the metal_radical magnetic coupling are discussed. Molecular magnetic project of nitroxide_metal complexes has made fruitful achievements, but crystal magnetic project is difficult to be controlled, and it is a challenge to chemists. The studies on nitronyl nitroxide_metal complexes are summarized. At present, there are three major approaches to increasing the T c of the metal_radical compounds: (ⅰ) Searching for nitronyl nitroxide ligands that can yield 3_D ferro_ or ferrimagnetic structures; (ⅱ) decorating the structure of radicals with the aim to enhance the coordinate capability of radicals; (ⅲ) grafting polynitroxide radicals as a versatile bridge. The third approach, namely searching for polynitroxide ligand, will serve as a hopeful strategy for exploring higher T c radical molecule_based magnets.     

Y(Fe1-xCox)11.3Nb0.7化合物的室温饱和磁化强度Ms和室温各向异性场Ba

用脉冲强磁场测量法和奇点探测法 (SPD) ,研究了电弧炉熔炼方法制备的 1∶12型稀土过渡族金属间化合物Y(Fe1 -xCox) 1 1 .3Nb0 .7(x =0 .0 0 ,0 .0 5,0 .10 ,0 .15,0 .2 0 )多晶样品的室温磁特性 .研究结果表明 ,Y(Fe1 -xCox) 1 1 .3Nb0 .7系列化合物的室温 (30 0K)各向异性场Ba 和饱和磁化强度Ms,随Co含量的增加 ,都先增加后降低 .     

用Co、Ni或Co、Al取代Nd-Fe-B磁体中部分Fe的研究

本文分别用 Co、Ni 及 Co、Al 取代 Nd-Fe-B 中部分 Fe,取代形式为Nd_(17),Fe_(75.5-2x)Co_xNi_xB_(7.5)及 Nd_(17)Fe_(75.5-2x)Co_xB_(7.5)(x 在1～5间变化),对Nd-Fe-B 磁体的磁性及热稳定性进行了研究.随着 Co、Ni 量的增加,磁体的居里温度提高,磁感温度系数降低.随着 Co、Al 量的增加,在不降低 Nd-Fe-B 磁体居里温度的情况下,使磁体总损失大幅度降低,_1H_c 显著提高,可获得大矫顽力 Nd-Fe-B磁体。     

有序化对(Fe,Ni)3V合金环境氢脆的影响

研究了室温下不同有序度的(Fe,Ni)3V在真空、空气和氢气中的力学性能.结果表明不同有序度的(Fe,Ni)3V均不存在空气中水气诱发的环境氢脆;无序态(Fe,Ni)3V在氢气环境下存在轻微的脆性;而有序态在氢气中有强烈的脆化作用,其脆性随有序化程度提高而增加.扫描电镜观察表明无序态合金在不同气氛中断裂时全部为韧性断口;有序态合金在空气和真空中基本上也为穿晶韧性断口,但在氢气中的断口形貌大部分为脆性断口.     

钙钛矿La0.7Pb0.3MnO3的结构和磁性研究

采用固相反应烧结法成功制备了单相多晶样品La0．7Pb0.3MnO3，用X射线衍射和超导量子干涉仪及振动样品磁强计对其结构和磁性进行了研究。结果表明，样品呈菱面相晶体结构，空间群为R-3C，居里温度Tc=348K，在居里温度附近，发生铁磁一顺磁转变。此材料呈现出一种典型的团簇玻璃特性，其阻截温度为336K，并且对零场冷却和场冷却曲线给出了合理的解释。室温下，其矫顽力只有40Oe。     

Decoherence in crystals of quantum molecular magnets

Quantum decoherence is a central concept in physics. Applications such as quantum information processing depend on understanding it; there are even fundamental theories proposed that go beyond quantum mechanics, in which the breakdown of quantum theory would appear as an 'intrinsic' decoherence, mimicking the more familiar environmental decoherence processes. Such applications cannot be optimized, and such theories cannot be tested, until we have a firm handle on ordinary environmental decoherence processes. Here we show that the theory for insulating electronic spin systems can make accurate and testable predictions for environmental decoherence in molecular-based quantum magnets. Experiments on molecular magnets have successfully demonstrated quantum-coherent phenomena but the decoherence processes that ultimately limit such behaviour were not well constrained. For molecular magnets, theory predicts three principal contributions to environmental decoherence: from phonons, from nuclear spins and from intermolecular dipolar interactions. We use high magnetic fields on single crystals of Fe(8) molecular magnets (in which the Fe ions are surrounded by organic ligands) to suppress dipolar and nuclear-spin decoherence. In these high-field experiments, we find that the decoherence time varies strongly as a function of temperature and magnetic field. The theoretical predictions are fully verified experimentally, and there are no other visible decoherence sources. In these high fields, we obtain a maximum decoherence quality-factor of 1.49?×?10(6); our investigation suggests that the environmental decoherence time can be extended up to about 500 microseconds, with a decoherence quality factor of ～6?×?10(7), by optimizing the temperature, magnetic field and nuclear isotopic concentrations.     

Ni50.3Mn27.3Ga22.4磁性形状记忆合金薄膜的磁场增强马氏体相变应变研究

采用磁控溅射方法制备Ni50.3Mn27.3Ga22.4磁性形状记忆合金薄膜。研究薄膜的晶体结构、磁化行为以及磁场对马氏体相变应变的影响。试验结果表明,经823 K退火1 h的Ni50.3Mn27.3Ga22.4薄膜,室温下处于奥氏体态,呈较强的(110)织构特性,且室温饱和磁化强度约为40 emμ/g。试验还发现,当沿膜面方向施加0到0.8 T磁场时,Ni50.3Mn27.3Ga22.4薄膜的马氏体相变应变量随磁场强度的增大而增大,呈现出磁场增强马氏体相变应变效应。     

Coexistence of ferromagnetism and metallic conductivity in a molecule-based layered compound

Crystal engineering--the planning and construction of crystalline supramolecular architectures from modular building blocks--permits the rational design of functional molecular materials that exhibit technologically useful behaviour such as conductivity and superconductivity, ferromagnetism and nonlinear optical properties. Because the presence of two cooperative properties in the same crystal lattice might result in new physical phenomena and novel applications, a particularly attractive goal is the design of molecular materials with two properties that are difficult or impossible to combine in a conventional inorganic solid with a continuous lattice. A promising strategy for creating this type of 'bi-functionality' targets hybrid organic/inorganic crystals comprising two functional sub-lattices exhibiting distinct properties. In this way, the organic pi-electron donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and its derivatives, which form the basis of most known molecular conductors and superconductors, have been combined with molecular magnetic anions, yielding predominantly materials with conventional semiconducting or conducting properties, but also systems that are both superconducting and paramagnetic. But interesting bulk magnetic properties fail to develop, owing to the discrete nature of the inorganic anions. Another strategy for achieving cooperative magnetism involves insertion of functional bulky cations into a polymeric magnetic anion, such as the bimetallic oxalato complex [MnIICrIII(C2O4)3]-, but only insoluble powders have been obtained in most cases. Here we report the synthesis of single crystals formed by infinite sheets of this magnetic coordination polymer interleaved with layers of conducting BEDT-TTF cations, and show that this molecule-based compound displays ferromagnetism and metallic conductivity.     

放电等离子烧结热变形Nd-Fe-B磁体的磁性能研究

采用放电等离子烧结技术,利用不同速率的快淬薄带制备出各向异性的热变形Nd-Fe-B磁体,运用振动样品磁强计和扫描电子显微镜对热变形磁体的磁性能和微观结构进行研究.结果表明：随着快淬薄带速率的增加,获得最佳磁性能的热变形温度也逐渐增加,三类热变形Nd-Fe-B磁体获得最佳磁性能的热变形温度分别为650,680和700°C;磁体最佳磁性能中的剩磁和最大磁能积随着快淬薄带速率的增加而降低,而内禀矫顽力却略有增加.磁体的晶粒尺寸随着热变形温度的增加而增大;相同热变形温度下,磁体的晶粒尺寸随快淬速率的增加而减小.     

磁控溅射涂层的耐蚀性

通过采用磁控溅射工艺,将两种铁基和镍基材质的靶材溅射到基材(1Cr18Ni9Ti)上,形成4种薄膜。对靶材、基材和薄膜等分别在不同浓度硫酸中的耐腐蚀性进行了测量,并对薄膜在0.05mol/L硫酸中的耐点蚀性进行了研究。通过对Tafel曲线、循环极化曲线及显微组织的分析,结果表明:溅射后薄膜组织为微晶,薄膜的耐蚀性普遍比溅射材前靶的耐蚀性要好;薄膜耐点蚀性很好。