金属富勒烯的质谱研究

利用电弧放电法合成笼内金属富勒烯 Gd@C82 ,Gd2 @C80 ,Gd@C80 .实验结果表明 ,两步高温高压法( 1 ,2 ,4 -三甲基苯 ,吡啶 )可有效地提取金属富勒烯 Gd@C82 .本文分别利用 ESI-MS,REC-MS,MALDI-TOF-MS质谱技术研究了 Gd@C82 ,Gd2 @C80 ,Gd@C80 和富勒烯 Cn( n=60 ,70 ,82 ,84… )的气相负离子特性 .结果表明 ,包入 Gd3 + 后非极性的 C82 转变为极性的 Gd@C82 分子 ;金属离子 Gd3 + 处于 C3 -82 笼中非中心的位置 .

High-temperature and high-pressure extraction of Ln(n)@C-2n(Ln=Y,Gd,Tb)

A high temperature and high pressure method was used to efficiently and selectively extract metallofullerenes Ln(m)@C-2n,(Ln = Y, Gd, Tb) in a closed stainless steel autoclave under inert gas protection. 1, 2, 3-Trichlorobenzene was found to be more effective and selective for the extraction of Ln@C-82 (Ln=Y, Gd, Tb) from empty fullerenes and other metallofullerene species.

High-temperature, high-pressure extraction of metallofullerenes Gd@C-2n

A high-temperature, high-pressure extraction technique with toluene and pyridine were employed for the extraction of metallofullerenes Gd@C-2n, A series of Gd@C-2n for 2n from 70 to 96 were effectively extracted by toluene. Gd@C-74 was shown to be a new stable soluble metallofullerene species. Pyridine was found to be more useful for the extraction of Gd@C-82 and Gd-2@C-80 from empty fullerenes and other metallofullerene species.

Kinetics of Glass Transition and Crystallization in Carbon Nanotube Reinforced Mg-Cu-Gd Bulk Metallic Glass

Mg65 Cu25 Gdlo bulk metallic glass and its carbon nanotube reinforced composite were prepared. Differential scanning calorimeter (DSC) was used to investigate the kinetics of glass transition and crystallization processes. The influence of CNTs addition to the glass matrix on the glass transition and crystallization kinetics was studied. It is shown that the kinetic effect on glass transition and crystallization are preserved for both the monothetic glass and its glass composite. Adding CNTs in to the glass matrix reduces the influence of the heating rate on the crystallization process. In addition, the CNTs increase the energetic barrier for the glass transition. This results in the decrease of GFA . The mechanism of the GFA decrease was also discussed.

(Ga, Gd, As) film growth on GaAs substrate by low-energy ion-beam deposit

(Ga, Gd, As) film was fabricated by the mass-analyzed dual ion-beam epitaxy system with the energy of 1000 eV at room temperature. There was no new peak found except GaAs substrate peaks (0 0 2) and (0 0 4) by X-ray diffraction. Rocking curves were measured for symmetric (0 0 4) reflections to further yield the lattice mismatch information by employing double-crystal X-ray diffraction. The element distributions vary so much due to the ion dose difference from AES depth profiles. The sample surface morphology indicates oxidizing layer roughness is also relative to the Gd ion dose, which leads to islandlike feature appearing on the high-dose sample. One sample shows ferromagnetic behavior at room temperature. (C) 2003 Elsevier B.V. All rights reserved.

低能离子束沉积制备GaAs:Gd的研究

对室温条件下用低能离子束沉积得到的 Ga As∶ Gd样品 ,借助 X射线衍射 (XRD)和高分辨 X射线衍射 (HR-XRD)进行了结构分析 ,结果表明没有出现新的衍射峰 ,并且摇摆曲线的形状与 Gd的注入计量密切相关 .运用 X光电子能谱仪对比分析了 Gd注入后 ,衬底中主要元素 Ga2 p和 As3d的化学位移 ,以及不同计量的样品中注入的Gd4 d芯能级束缚能的变化 ,并分析了铁磁性产生的可能原因 .

低能离子束制备(Ga,Gd,As)薄膜

室温条件下 ,用离子束外延设备制备 ( Ga,Gd,As)样品 ,X射线衍射 ( XRD)结果表明除了 Ga As衬底峰 ,没有发现其他新相的衍射峰。俄歇电子能谱 ( AES)分析了样品中元素随深度的变化 ,不同样品中元素的分布有着不同的特点。并运用原子力显微镜 ( AFM)研究了样品表面的形貌特点 ,表明样品表面的粗糙度与 Gd注入过程中在样品表面沉积的多少有关。运用交变梯度磁强计 ( AGM)对薄膜进行磁性分析 ,结果表明有的样品在室温条件下出现铁磁性 ,但金属钆本身具有室温铁磁性 ,因而需要进一步分析。

离子束外延制备GaAs:Gd薄膜

　室温条件下,用低能离子束外延制备了GaAs∶Gd薄膜,X射线衍射(XRD)结果表明除了GaAs衬底峰没有发现其它新相的衍射峰,并借助于高分辨X射线衍射(HR XRD)进一步分析了晶格常数的变化特点。俄歇电子能谱(AES)分析了样品表面的成分,及元素随深度的分布规律,在60nm深处元素的相对含量发生明显改变,运用原子力显微镜(AFM)揭示了样品表面的形貌特点。

Growth and spectral properties of Er:Gd2SiO5 crystal

Er3+ -doped Gd2SiO5 (Er:GSO) single crystal with dimensions of circle divide 35 x 40 mm(3) has been grown by the Czochralski method. The absorption and fluorescence spectra of the Er:GSO crystal were measured at room temperature. The spectral parameters were calculated based on Judd-Ofelt theory, and the intensity parameters Omega(2), Omega(4) and Omega 6 are obtained to be 6.168 x 10(-20), 1.878 x 10(-20), and 1.255 x 10(-20) cm(2), respectively. The emission cross-section has been calculated by Fuechtbauer-Ladenbury formula. (c) 2007 Elsevier B.V. All rights reserved.

Magnetic coupling properties of rare-earth metals (Gd, Nd) doped ZnO: First-principles calculations

The electronic structure and magnetic coupling properties of rare-earth metals (Gd, Nd) doped ZnO have been investigated using first-principles methods. We show that the magnetic coupling between Gd or Nd ions in the nearest neighbor sites is ferromagnetic. The stability of the ferromagnetic coupling between Gd ions can be enhanced by appropriate electron doping into ZnO Gd system and the room-temperature ferromagnetism can be achieved. However, for ZnO Nd system, the ferromagnetism between Nd ions can be enhanced by appropriate holes doping into the sample. The room-temperature ferromagnetism can also be achieved in the n-conducting ZnO Nd sample. Our calculated results are in good agreement with the conclusions of the recent experiments. The effect of native defects (V-Zn, V-O) on the ferromagnetism is also discussed. (C) 2009 American Institute of Physics. [DOI 10.1063/1.3176490]

Anomalous temperature dependence of photoluminescence from stoichiometric GD(2)O(3-x) film

A stoichiometric Gd2O3-x thin film has been grown on a silicon (10 0) substrate with a low-energy dual ion-beam epitaxial technique. Gd2O3-x shares Gd2O3 structures although there are many oxygen deficiencies in the film. The photoluminescence (PL) measurements have been performed in a temperature range 5-300 K. The detailed characters of the peak position, the full-width at half-maximum (FWHM) and the peak intensity at different temperature were reported. An anomalous intensity behavior of the PL spectra has been observed, which is similar to that of some other materials such as porous silicon and silicon nanocrystals in silicon dioxide. Therefore, we suggest that the nanoclusters with the oxygen deficiencies contribute to the PL emission and employ the model of singlet-triplet exchange splitting of exciton to discuss the four peaks observed in the experiment. (C) 2003 Elsevier B.V. All rights reserved.

(Ga, Gd, As) film growth on GaAs substrate by low-energy ion-beam deposit

(Ga, Gd, As) film was fabricated by the mass-analyzed dual ion-beam epitaxy system with the energy of 1000 eV at room temperature. There was no new peak found except GaAs substrate peaks (0 0 2) and (0 0 4) by X-ray diffraction. Rocking curves were measured for symmetric (0 0 4) reflections to further yield the lattice mismatch information by employing double-crystal X-ray diffraction. The element distributions vary so much due to the ion dose difference from AES depth profiles. The sample surface morphology indicates oxidizing layer roughness is also relative to the Gd ion dose, which leads to islandlike feature appearing on the high-dose sample. One sample shows ferromagnetic behavior at room temperature. (C) 2003 Elsevier B.V. All rights reserved.

Mossbauer spectroscopic study of R3Fe29-xCrx and R3Fe29-xCrxH,(y)(R = Y, Ce, Nd, Sm, Gd, Tb, and Dy)

Fe-57 Mossbauer spectra for the series of R3Fe29-xCrx (R = Y,Ce, Nd, Sm, Gd, Tb, and Dy) compounds and their hydrides have been measured at 4.2 K. The weighted average hyperfine field at the Fe sites was separated into a 3d-electron contribution, proportional to the average Fe moment, and a transferred contribution due to rare earth moments. The latter was found to increase with the rare earth effective spin (g(J) - 1) J. Hyperfine fields in the hydrides were only slightly larger than in the corresponding alloys.

Fe-57 Mossbauer spectroscopic and magnetic studies of R3Fe29-xVx (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy)

Mossbauer spectra for Fe atoms in the series of R3Fe29-xVx (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy) compounds were collected at 4.2 K. The ratio of 14.5 T/mu(B) between the average hyperfine field B-hf and the average Fe magnetic moment mu(Fe)(MS), obtained from our data, in Y3Fe29-xVx is in agreement with that deduced from the RxTy alloys by Gubbens et al. The average Fe magnetic moments mu(Fe)(MS) in these compounds at 4.2 K, deduced from our Mossbauer spectroscopic studies, are in accord with the results of magnetization measurement. The average hyperfine field of the Fe sites for R3Fe29-xVx at 4.2 K increases with increasing values of the rare earth effective spin (g(J) - 1) J, which indicates that there exists a transferred spin polarization induced by the neighboring rare earth atom.

Mossbauer spectroscopy study of Fe-57 in R3Fe29-xTx (R=Y, Ce, Nd, Sm, Gd, Tb and Dy; T=V and Cr)

Fe-57 Mossbauer spectra for the Fe atoms in the R3Fe29-xTx (R=Y, Ce, Nd, Sm, Gd, Tb, Dy; T=V, Cr) compounds were collected at 4.2 K. The analysis of Mossbauer spectra was based on the results of magnetization and neutron powder diffraction measurements. The average Fe magnetic moments at 4.2 K, deduced from our data, are in accord with magnetization measurements. The average hyperfine field of Tb3Fe29-xCrx (x=1.0, 1.5, 2.0, and 3.0) decreases with increasing Cr concentration, which is also in accordance with the variation of the average Fe magnetic moment in the Tb3Fe29-xCrx compounds.