Solvothermal synthesis of nanocrystalline zinc oxide doped with Mn2+, Ni2+, Co2+ and Cr3+ ions

ZnO nanopowders doped with Mn²⁺, Ni²⁺, Co²⁺ and Cr³⁺ ions have been synthesised for the first time using a solvothermal reaction with microwave heating. The nanopowders were produced from a solution of zinc acetate and manganese (II), chromium (III), nickel (II) and cobalt (II) acetates, using ethylene glycol as a solvent. The content of Ni²⁺, Co²⁺ and Cr³⁺ ions in the solution and in the solid phase were close to each other up to 5 mol%. The doping level of Mn²⁺ ions in the solid is about 50% of that in the solution. No phases or compounds other than ZnO were detected by X-ray diffraction with Mn²⁺, Co²⁺ and Ni²⁺ doping. With Cr³⁺ ions a small amount of chromium oxide was found. None of the powders displayed any luminescence after doping. The Mn²⁺-doped powder displayed a paramagnetic behaviour. ESR and magnetisation investigations have revealed that no clustering of Mn²⁺ ions occurred up to a doping level of 3.9 mol%. The average grain size of powders doped with Ni²⁺, Cr³⁺, Co²⁺ and Mn²⁺ for a 10 mol% ion content in the solution was about 20 nm and the grain size dispersion 30%. With increasing dopant content the grain size decreased. It appears that the solvothermal process employed allows relatively high doping levels of the transition metal ions to be achieved without any dopant clustering or oxide precipitation.     

Local structure of Co and Ni in decagonal AlNiCo investigated by polarized EXAFS

The local structure of cobalt and nickel in single crystals of decagonal quasicrystals with composition Al_71.5Ni_15.5Co₁₃ and Al₇₅Ni_14.5Co_10.5 have been studied by polarized EXAFS. Significant differences between the Ni and Co local environments have been detected. The effective absence of the 4 ? periodicity along the decagonal axis in these QCs is confirmed and indications about its reasons are presented. Received 26 July 2000 and Received in final form 20 October 2000     

Local structure of Ni2Si

The local structure around the Ni atom in Ni₂Si has been studied by measuring and analyzing the Extended Energy Loss Fine Structure above the Ni M_2,3 edge. The radial distribution function we found is characterized by the efficiency of the only nearest neighbours Si atoms. We also obtained the phase shift of the Ni-Si pair and the backscattering amplitude.     

An EPR study of Ni+ centers in SrF2:Ni and BaF2:Ni

An EPR study of RT X-irradiated SrF2:Ni and BaF2:Ni has been performed. Different kinds of Ni⁺ centers showing small deviations with respect to a basic structure have been observed. This basic structure consists of a Ni⁺ ion displaced along a <100> direction from the cation substitutional position toward the center of a face of the cube of fluorines. These results are similar to those previously reported on CaF2:Ni.

The spin Hamiltonian parameters of the different centers obtained from the analysis of the corresponding rotational diagrams are also reported.     

Magnetic sublattices in Np2Co17 and Np2Ni17

Rare-earth-based compounds R₂T₁₇ (R=Rare earth; T=Transition metal) have been extensively studied and developed for applications as permanent magnets. The actinide-based analogues, however, are much less documented and we report here about the magnetic properties of Np₂Co₁₇ and Np₂Ni₁₇, as inferred from ²³⁷Np Mössbauer spectroscopy, the best resonance in actinides, and specific heat.     

Co2+ and Mn2+ ion locations in doped CsCdCl3

Summary Substitutional Co²⁺ and Mn²⁺ ions at the two different Cd sites in the compound CsCdCl₃ have been studied by using electron paramagnetic resonance. The preferential occupation, Co²⁺ in the Cd_II site, Mn²⁺ in the Cd_I site, is discussed in terms of crystallochemical symmetry arguments. Paper presented at the ?V International Conference on Ternary and Multinary Compounds?, held in Cagliari, September 14–16, 1982.     

RbMgF3 ：Ni2+ 体系晶格局域结构的EPR理论研究

在考虑掺杂晶体局域畸变的影响后, 建立了联系RbMgF₃: Ni²⁺体系的局域畸变结构与EPR谱间的关系, 并计算了RbMgF₃: Ni²⁺晶体在C_3v和D_3d对称下的零场分裂参量和g 因数. EPR谱的理论计算值与实验值符合甚好.      

CASPT2 study on low-lying states of HBS+ and HSB+ cations

Some low-lying states of the nine-valence-electron systems HBS⁺ and HSB⁺ cations have been studied by large-scale theoretical calculations using three methods CASSCF, CASPT2, and DFT B3LYP with the contracted atomic natural orbital and cc-pVTZ basis sets. The geometries of all stationary points along the potential energy surfaces were optimized and the energies were calculated. The potential energy curves of isomerization reactions between HBS⁺ and HSB⁺ were calculated as a function of HBS bond angle. The calculated results indicated that the ground-state HBS⁺ is linear, while the ground-state HSB⁺ is bent, which is in contradiction to Walsh's rules predicting linear structures for the HXY systems containing 10 or less valency electrons.     

ZnS:Co2+和CdTe:Co2+中配体对g因子的贡献

采用双自旋-轨道耦合模型和分子轨道研究了Co²⁺离子在Ⅱ-Ⅵ半磁半导体ZnS和CdTe中的EPR g因子.计算表明,配体Te有大的SO耦合作用和强的共价性,其对g因子有较大的贡献.     

Mononuclear Co(III) and Ni(II) Complexes with Polypyridyl Ligands, [Co(phen)2(taptp)]3+ and [Ni(phen)2(taptp)]2+: Synthesis, Photocleavage and DNA-binding

Two novel, mixed ligand complexes of cobalt(III) and nickel(II), [Co(phen)₂(taptp)]³⁺ (1) and [Ni(phen)₂(taptp)]²⁺ (2) (phen = 1,10-phenanthroline and taptp = 4,5,9,18-tetraazaphenanthreno [9,10-b]triphenylene), were synthesized and characterized by elemental analyses, UV-visible and NMR spectroscopies. The binding interactions of the two complexes with DNA have been investigated using absorption and emission spectroscopy methods and electrophoresis measurement mode. The intrinsic binding constants for these complexes to DNA are in the order of 10⁵. In Tris buffer, the Co(III) complex shows a moderate luminescence which was enhanced after binding to DNA. However for complex Ni(II), no emission was observed in Tris buffer. The [Co(phen)₂(taptp)]³⁺ and [Ni(phen)₂(taptp)]²⁺ can cause the photocleavage of DNA supercoiled pBR322 upon irradiation by 360 nm light. Based on the data, an intercalative mode of DNA binding is suggested for the two complexes.     

Calculation of the 0+ and 2+ giant resonances in Ni58

Estimates of the excitation energy, width and sum rule fraction of the collective monopole and quadrupole vibrations indicate that the peak in the 62A ^?1/3 MeV region is a superposition of the 0⁺ and 2⁺ modes.     

Magnetic properties of TiO2 rutile implanted with Ni and Co

Single crystals of TiO₂ rutile were implanted with high fluences of Co and Ni ions, aiming at the understanding of the role of these ions in the magnetic properties of the doped oxide. Magnetization and electrical resistivity results as a function of temperature and magnetic field are presented and correlated with information obtained by Rutherford backscattering spectrometry measurements in the same samples.     

Local structure and magnetism of Fe, Co and Ni doped Cr3Si

The lattice site occupation of 3d-type impurities in Cr₃Si doped with Fe, Co and Ni were studied using the Extended X-ray Absorption Fine Structure (EXAFS) technique, X-rays and magnetic susceptibility measurements. The EXAFS measurements were performed particularly carefully on the K-edge of chromium and cobalt. EXAFS data strengthened by simulations of the spectra show unambiguously that the impurities are occupying mostly Cr-sites. The magnetic state of the alloys has been studied theoretically using the Wien2k code. It is observed that if calculations are not carried out on an appropriately fine mesh of points in k-space, one can get the result indicating ferromagnetism although the overall magnetic moment per formula unit is weak.     

Electrical properties of ferromagnetic Ni2MnGa and Co2CrGa Heusler alloys

The electrical properties of ferromagnetic Ni₂MnGa and Co₂CrGa Heusler alloys are measured in the temperature range 4–900 K. The effect of the energy gap near the Fermi level in the electronic spectrum on the behavior of electrical resistivity and absolute differential thermopower is discussed.     

Electronic pair excitations of Mn2+ and Ni2+ in perovskite fluorides: involvement of the 3 T 1g a state of Ni2+

Crystals of KZnF₃ and KMgF₃ doped with Mn²⁺ and Ni²⁺ were used to study the spectroscopic properties of Mn²⁺-F^--Ni²⁺ pairs. Pair transitions to the doubly excited states ⁴ E_g ^a , ⁴ A _1g (Mn)³ T _1g ^a (Ni) and ⁴ E_g ^b (Mn)³ T _1g ^a (Ni) were observed. The participation of the spin-allowed ³ A _2g →³ T _1g ^a excitation on Ni²⁺ in the pair transition is explained by spin-orbit mixing between ³ T _1g ^a and ¹ E_g . The prominent electronic origins are assigned to the double spin-flip transitions ⁶ A _1g (Mn)³ A _2g (Ni) →⁴ E_gu(Mn)³ T _1g ^a (Γ₃)v(Ni) and ⁴ A _1g (Mn)³ T _1g ^a (Γ₃)v(Ni). The former lie at lower energy and are more intense than the corresponding ⁶ A _1g (Mn)³ A _2g (Ni) →⁴ E_gv(Mn)³ T _1g ^a (Γ₃)u(Ni) transitions involving two orbital jumps. The well-resolved vibronic structure is composed of three basic vibrations of ～ 150 cm^-1, ～ 294 cm^-1 and ～ 508 cm^-1 in the KZnF₃ host.     

用光谱和EPR谱确定CsMgBr3:Ni2+的局域结构

本文采用半自洽场(semi-SCF)自由Ni2 的3d轨道波函数、点电荷—偶极子模型和Ni2 -6X-(X=F,Cl,Br,I)络合物的μ-κ-α模型,建立了结构参数与光谱、EPR谱之间的定量关系,利用完全对角化方法,由光谱和电子顺磁共振(EPR)谱,确定了CsMgBr3:Ni2 晶体在77K温度时的局域结构参数,统一解释了CsMgBr3:Ni2 晶体的局域结构、光谱和EPR谱。所得理论结果与实验值符合得很好。此外,还讨论了晶体局域结构发生畸变的原因。