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1.
Magnetic and spectroscopic properties of the planar antiferromagnet K2FeF4 are determined by the Fe2+ ions at tetragonal sites. The two-dimensional easy-plane anisotropy exhibited by K2FeF4 is due to the zero field splitting (ZFS) terms arising from the orbital singlet ground state of Fe2+ ions with the spin S=2. To provide insight into the single-ion magnetic anisotropy of K2FeF4, the crystal field theory and the microscopic spin Hamiltonian (MSH) approach based on the tensor method is adopted. Survey of available experimental data on the crystal field energy levels and free-ion parameters for Fe2+ ions in K2FeF4 and related compounds is carried out to provide input for microscopic modeling of the ZFS parameters and the Zeeman electronic ones. The ZFS parameters are expressed in the extended Stevens notation and include contributions up to the fourth-order using as perturbation the spin-orbit and electronic spin-spin couplings within the tetragonal crystal field states of the ground 5D multiplet. Modeling of the ZFS parameters and the Zeeman electronic ones is carried out. Variation of these parameters is studied taking into account reasonable ranges of the microscopic ones, i.e. the spin-orbit and spin-spin coupling constants, and the energy level splittings, suitable for Fe2+ ions in K2FeF4 and Fe2+:K2ZnF4. Conversions between the ZFS parameters in the extended Stevens notation and the conventional ones are considered to enable comparison with the data of others. Comparative analysis of the MSH formulas derived earlier and our more complete ones indicates the importance of terms omitted earlier as well as the fourth-order ZFS parameters and the spin-spin coupling related contributions. The results may be useful also for Fe2+ ions at axial symmetry sites in related systems, i.e. Fe:K2MnF4, Rb2Co1−xFexF4, Fe2+:Rb2CrCl4, and Fe2+:Rb2ZnCl4.  相似文献   

2.
Pristine and Au-covered molecular films have been analyzed by ToF-SIMS (TRIFT™), using 15 keV Ga+ (FEI) and 15 keV C60+ (Ionoptika) primary ion sources. The use of C60+ leads to an enormous yield enhancement for gold clusters, especially when the amount of gold is low (2 nmol/cm2), i.e. a situation of relatively small nanoparticles well separated in space. It also allows us to extend significantly the traditional mass range of static SIMS. Under 15 keV C60+ ion bombardment, a series of clusters up to a mass of about 20,000 Da (Au100: 19,700 Da) is detected. This large yield increase is attributed to the hydrocarbon matrix (low-atomic mass), because the yield increase observed for thick metallic films (Ag, Au) is much lower. The additional yield enhancement factors provided by the Au metallization procedure for organic ions (MetA-SIMS) have been measured under C60+ bombardment. They reach a factor of 2 for the molecular ion and almost an order of magnitude for Irganox fragments such as C4H9+, C15H23O+ and C16H23O.  相似文献   

3.
杨子元  郝跃 《物理学报》2005,54(6):2883-2892
基于完全对角化方法,研究了4B1(3d3)态 离子在四角对称晶场中的磁相互作用,分析了自旋哈密顿参量(b02, g, g, Δg)的微观起源.结果表明 :在被考虑的大部分晶场区域,人们通常考虑的SO(spin-orbit)磁相互作用的贡献最为重要 ;然而,对于零场分裂参量b02而言,来自其他机理(包 括SS(spin-orbit),SOO(sp in-other-orbit),SO-SS-SOO)的贡献在大部分晶场区域超过了20%;在部分晶场区域,其 他机理的贡献甚至超过SO机理的贡献.详细地分析了Macfarlane 零场分裂参量b02 近似三阶微扰理论的收敛性,结果表明:该理论在大部分晶场区域收敛性较差.讨论了3d3态离子第一激发态2Eg分裂的微观起源.并利用 群论方法解 释了在C4v和C3v对称晶场中2Eg< /sub>态分裂的不同机理. 关键词: 4B1(3d3)态离子')" href="#">4B1(3d3)态离子 磁相互作用 自旋哈密 顿参量 完全对角化方法(CDM) 微扰理论方法(PTM)  相似文献   

4.
Raman spectra from the first Ti fullerene complex Cp 2Ti(η2-C60) · C6H5CH3 are presented. Compared to spectra of pure C60, the spectra of the Ti complex exhibit a number of new peaks due to the symmetry lowering for C60. The A g(2) mode is downshifted by 12 cm−1 compared to C60, which corresponds to a charge transfer of one electron per Ti-C60 bond. This value (6 cm−1 for one transferred electron) is identical to the downshift of the A g(2) mode in alkali metal fullerides with ionic bonding. The spectra of Cp 2Ti(η2-C60) · C6H5CH3 were compared to the spectra of evaporated TixC60 films. The A g(2) mode in Ti4C60 showed a downshift of about 25 cm−1 compared to pure C60, which corresponds to a charge transfer of one electron per Ti atom; this is similar to the ionic alkali metal fullerides and different from η2-C60-type bonding. From Fizika Tverdogo Tela, Vol. 44, No. 3, 2002, pp. 483–485. Original English Text Copyright ? 2002 by Talyzin, Jansson, Usatov, Burlakov, Shur, Novikov. This article was submitted by the authors in English.  相似文献   

5.
EPR spectra of Mn2+ in MgF2 crystals grown by the Bridgman technique were measured at 300 and 20 K. Application of the superposition model to the zero field splitting (ZFS) patterns indicates complete absence of dynamic contributions to the ZFS. The luminescence spectra are also in accord with substitutional incorporation of Mn2+.  相似文献   

6.
The local structure distortion and the spin Hamiltonian (SH) parameters, including the zero-field splitting (ZFS) parameter D and the Zeeman g-factors g and g, are theoretically investigated by means of complete diagonalization method (CDM) and the microscopic spin Hamiltonian theory for tetragonal charge compensation CrF5O defect center in Cr3+:KMgF3 crystals. The superposition model (SPM) calculations are carried out to provide the crystal field (CF) parameters. This investigation reveals that the replacement of O2− for F and its induced lattice relaxation Δ1(O2−) combined with an inward relaxation of the nearest five fluorine Δ2(F) give rise to a strong tetragonal crystal field, which in turn results in the large ZFS and large anisotropic g-factor Δg. The experimental SH parameters D and Δg can be reproduced well by assuming that O2− moves towards the central ion Cr3+ by Δ1(O2−)=0.172R0 and the five F ions towards the central ion Cr3+ by Δ2(F)=0.022R0. Our approach takes into account the spin-orbit (SO) interaction as well as the spin-spin (SS), spin-other-orbit (SOO), and orbit-orbit (OO) interactions omitted in previous studies. This shows that although the SO interaction is the most important one, the contributions to the SH parameters from other three magnetic interactions are appreciable and should not be omitted, especially for the ZFS parameter D.  相似文献   

7.
In the present study, SF5+ and C60+ were used as primary ions for sputtering and Bi3+ was used as primary ions for analysis. The depth profiling procedure was utilized to make 3D images of the chemistry of single cultured cells and tissue samples of intact intestinal epithelium.The results show sputtering of organic material from cells and tissue with both SF5+ and C60+ sources. Cholesterol fragments were found in the superficial layers when sputtering with C60+. Spectra were collected revealing the change in yield along the z-axis of the sample. 3D images of the localization of Na, K, phosphocholine and cholesterol were constructed with both ion sources for single cell cultures and the mouse intestine.Cryostate sections of mouse intestine were analysed in 2D and the results were compared with the 3D image of the intestine. The localization of cholesterol and phosphocholine was found to be similar in cryostate sections analysed in two dimensions and the sputtered, freeze-dried intestine analysed in 3D. The comparison of 2D and 3D images suggest that the phosphocholine signal faded with C60+ sputtering. In conclusion, both C60+ and SF5+ can be used as primary ion sources for sputtering of organic material from cells and tissues. Consecutive analysis with a Bi3+ source can be used to obtain image stacks that could be used for reconstruction of 3D images.  相似文献   

8.
The authors experimentally observed the superluminal propagation at negative group velocity in C60 polymethyl methacrylate (PMMA) firstly. The largest time advancement of 7.61 ms was obtained at 1 mg/cm3 of sample concentration, the corresponding group velocity was −0.657 m/s. Fast light in C60 PMMA offers several advantages over liquids or vapors for a variety of possible applications: (i) easy for experimental measurement and practical applications (ii) easy for manufacture, (iii) sample concentration is another convenient parameter to vary the signal delay.  相似文献   

9.
The secondary ion mass spectrum of silicon sputtered by high energy C60+ ions in sputter equilibrium is found to be dominated by Si clusters and we report the relative yields of Sim+ (1 ≤ m ≤ 15) and various SimCn+ clusters (1 ≤ m ≤ 11 for n = 1; 1 ≤ m ≤ 6 for n = 2; 1 ≤ m ≤ 4 for n = 3). The yields of Sim+ clusters up to Si7+ are significant (between 0.1 and 0.6 of the Si+ yield) with even numbered clusters Si4+ and Si6+ having the highest probability of formation. The abundances of cluster ions between Si8+ and Si11+ are still significant (>1% relative to Si+) but drop by a factor of ∼100 between Si11+ and Si13+. The probability of formation of clusters Si13+-Si15+ is approximately constant at ∼5 × 10−4 relative to Si+ and rising a little for Si15+, but clusters beyond Si15 are not detected (Sim≥16+/Si+ < 1 × 10−4). The probability of formation of Sim+ and SimCn+ clusters depends only very weakly on the C60+ primary ion energy between 13.5 keV and 37.5 keV. The behaviour of Sim+ and SimCn+ cluster ions was also investigated for impacts onto a fresh Si surface to study the effects that saturation of the surface with C60+ in reaching sputter equilibrium may have had on the measured abundances. By comparison, there are very minor amounts of pure Sim+ clusters produced during C60+ sputtering of silica (SiO2) and various silicate minerals. The abundances for clusters heavier than Si2+ are very small compared to the case where Si is the target.The data reported here suggest that Sim+ and SimCn+ cluster abundances may be consistent in a qualitative way with theoretical modelling by others which predicts each carbon atom to bind with 3-4 Si atoms in the sample. This experimental data may now be used to improve theoretical modelling.  相似文献   

10.
The damage characteristics of polyethylene terephthalate (PET) have been studied under bombardment by C60+, Au3+ and Au+ primary ions. The observed damage cross-sections for the three ion beams are not dramatically different. The secondary ion yields however were significantly enhanced by the polyatomic primary ions where the secondary ion yield of the [M + H]+ is on average 5× higher for C60+ than Au3+ and 8× higher for Au3+ than Au+. Damage accumulates under Au+ and Au3+ bombardment while C60+ bombardment shows a lack of damage accumulation throughout the depth profile of the PET thick film up to an ion dose of ∼1 × 1015 ions cm−2. These properties of C60+ bombardment suggest that the primary ion will be a useful molecular depth profiling tool.  相似文献   

11.
用角积分紫外光电子能谱技术测量了Yb2.75C60薄膜的价带电子态密度分布.相纯Yb2.75C60样品通过C1s芯态x射线电子谱峰的位移表征.结果表明Yb2.75C60是半导体,在费米能级处几乎没有电子态分布.Yb 6s电子态和C60LUMO能带的杂化效应不可忽略,有部分Yb 6s电子分布在Yb-C60杂化能带上. 关键词: 2.75C60')" href="#">Yb2.75C60 电子能谱 电子态密度  相似文献   

12.
Effects of platinum silicon, graphite and PET substrates on the secondary ion yield of sub-monolayer and multilayer samples of Cyclosporin A following 20 keV Au+, Au3+and C60+ impacts have been investigated. The obtained results of sub-monolayer samples show that platinum enhances the yield of the pseudo-molecular ion following Au+ and Au3+ impacts due to the high density of the substrate that enables the energy of the primary ions to be deposited near the surface. C60+ impacts on sub-monolayer samples are less effective, but there is an enhancement on PET substrates. Impacts of 20 keV Au+ and Au3+ are not very efficient on multilayer samples. 20 keV C60+ impacts enhance the yields significantly, especially for the relatively high molecular weight [M+H]+ ion.  相似文献   

13.
蒋德琼  李敏惠  余万伦 《物理学报》1997,46(8):1625-1630
对氟钙钛矿晶体AMF3:Fe3+(A=K,Rb,Cs;M=Zn,Cd)四角对称占位的零场分裂(ZFS)进行分析,证实了晶格缺陷及畸变的存在.对ZFS参量随晶格畸变参量的变化关系进行了详细研究,考虑了缺陷及缺陷引起的晶格畸变两者的贡献,得出几种氟钙钛矿晶体的晶格畸变参量 关键词:  相似文献   

14.
Yb掺杂C60薄膜的x射线光电子能谱研究   总被引:1,自引:1,他引:0       下载免费PDF全文
在超高真空系统中制备了C60的Yb填隙化合物薄膜.用x射线光电子能谱研究了Yb和C60结合过程中C 1s,Yb 4f和Yb 4d的变化.利用Yb 4f和C 1s的谱峰强度确定出相纯样品的化学组分接近Yb2.75C60,这一结果与晶体x射线衍射结果一致.Yb 4f和Yb 4d的峰形与峰位表明化合物中Yb的价态为Yb2+.相纯样品(Yb2.75C60)的C 关键词: 60的Yb填隙化合物薄膜')" href="#">C60的Yb填隙化合物薄膜 x射线光电子能谱 Yb价态  相似文献   

15.
Sputtering of organic materials using a C60 primary ion beam has been demonstrated to produce significantly less accumulated damage compared to sputtering with monatomic and atomic-cluster ion beams. However, much about the dynamics of C60 sputtering remains to be understood. We introduce data regarding the dynamics of C60 sputtering by evaluating TOF-SIMS depth profiles of bulk poly(methyl methacrylate) (PMMA). Bulk PMMA provides an ideal test matrix with which to probe C60 sputter dynamics because there is a region of steady-state secondary ion yield followed by irreversible signal degradation. C60 sputtering of PMMA is evaluated as a function of incident ion kinetic energy using 10 keV C60+, 20 keV C60+ and 40 keV C60++ primary ions. Changes in PMMA chemistry, carbon accumulation and graphitization, and topography as a function of total C60 ion dose at each accelerating potential is addressed.  相似文献   

16.
周建林  牛巧利 《中国物理 B》2010,19(7):77305-077305
This paper reports that the n-type organic thin-film transistors have been fabricated by using C60 as the active layer and polystyrene as the dielectric.The properties of insulator and the growth characteristic of C60 film were carefully investigated.By choosing different source/drain electrodes,a device with good performance can be obtained.The highest electron field effect mobility about 1.15 cm 2 /(V·s) could reach when Barium was introduced as electrodes.Moreover,the C60 transistor shows a negligible 'hysteresis effect' contributed to the hydroxyl-free of insulator.The result suggests that polymer dielectrics are promising in applications among n-type organic transistors.  相似文献   

17.
李宏年 《物理学报》2004,53(1):248-253
在C60单晶超高真空解理面上制备C60的Rb填隙化合物薄膜.用同步辐射光电子能谱研究了相衍变过程.观察到对应于固溶相、Rb1C60和Rb3C60的电子态密度分布.当数纳米厚Rb3C60薄膜在C60单晶(111)解理面形成后,室温条件下进一步沉积Rb至样品表面不产生fcc到bct或bcc结构相变.C60 关键词: 4C60和Rb5C60吸附相')" href="#">金属性Rb4C60和Rb5C60吸附相 60单晶')" href="#">C60单晶 相衍变 同步辐射光电子能谱  相似文献   

18.
The profile of the energy deposition footprint is controlled during the C60+ erosion of Si surfaces by varying the incident energy and/or incident angle geometry. Sputter yield, surface topography, and chemical composition of the eroded surfaces were characterized using atomic force microscopy (AFM) and secondary ion mass spectrometry (SIMS). The experiments show that the 10 keV, 40° incident C60+ erosion of Si results in the formation of a C containing, mound-like structure on the solid surface. We find that the occurrence of this C feature can be avoided by increasing the incident energy of the C60+ projectile or by increasing the incident angle of the C60+ projectile. While both strategies allow for the Si samples to be eroded, the occurrence of topographical roughening limits the usefulness of C60+ in ultra-high resolution semiconductor depth profiling. Moreover, we find that the relative effect of changing the incident angle geometry of the C60+ projectile on the profile of the energy deposition footprint, and thus the sputter yield, changes according to the kinetic energy of the projectile and the material of the bombarded surface, a behavior that is quite different than what is observed for an atomic counterpart.  相似文献   

19.
In this letter, dispersion properties of low-frequency electrostatic waves in a C60 molecule are investigated. It is assumed that C60 molecule is charged due to the field emission, and hence the C60 molecule can be regarded as charged dust spheres surrounded by degenerate electrons and ions. We obtain the dispersion relation for the low-frequency electrostatic oscillations in the C60 molecule by using the quantum hydrodynamic model in conjunction with the Poisson equation.  相似文献   

20.
A quartz crystal microbalance (QCM) has been used to determine total-mass sputtering yields of PMMA films by 1-16 keV C60+,2+ ion beams. Quantitative sputtering yields for PMMA are presented as mass loss per incident ion Ym. Mass-lost rate QCM data show that a 13 keV C60 cluster leads to emission equivalent to 800 PMMA molecules per ion. The power law obtained for the increase in sputtering yield with primary ion energy is in good agreement those predicted by “thermal spike” regime and MD models, when crater sizes are used to estimate sputtering.  相似文献   

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