Large oscillator strength excitons in PbGa2S4 crystals

Exciton states with a large oscillator strength (transverse-longitudinal splitting of 50 meV) and binding energy of 290 meV have been observed in PbGa₂S₄ crystals. The ground exciton states are stable up to the room temperature. The ground (n = 1) exciton state and two excited (n = 2 and n = 3) states of the short-wavelength B-excitons series were observed at low temperature (T = 10 K). The ground (n = 1) and the excited (n = 2) states of the long-wavelength A-exciton series were also revealed. The exciton Bohr radius of the ground exciton state was determined to be 70 Å for the A-exciton and 10 Å for the B-exciton. The band splitting and the main parameters of excitons have been determined from the calculation of the reflectivity spectra contours. The group theory analysis of the band symmetry was performed and the scheme of bands responsible for exciton transitions in the center of the Brillouin zone was proposed.     

关于算子形式的Bohr不等式的推广

采用算子论中的方法和技巧,研究了Bohr不等式的有界线性算子形式的推广,并且给出一些算子不等式,这样对文[4-5]中的结果进行了推广.进一步研究了Bohr不等式在算子范数上的性质,推广了文[6]中的相关结果.     

物理学中的自然单位方法

分析了物理学中自然单位的特点，用自然单位方法给出了原子物理学中玻尔理论的全部结果．     

REBa_2Cu_3O_(7-δ)系超导体的磁矩效应

本文研究了HoBa_2Cu_3O_(7-δ)系氧化物陶瓷超导体的生成工艺;着重探讨了磁场成形及磁场烧结对RE(RE=Y,Ho)Ba_2Cu_3O_(7-δ)系氧化物超导体的取向及超导性能的影响;并借助于X—ray衍射分析和SEM分析,从金属离子外层电子状态对结果进行了探讨、分析。     

Practical calculations of stopping powers for intermediate energy electrons in some elemental solids

This study presents calculation results of the stopping power (SP) of electrons of kinetic energy from 10 eV to 100 keV for some elemental solids. The method is based on utilization of the modified Bethe-Bloch SP expression and analytical expression for effective atomic electron number and effective mean excitation energies of target atoms, and for effective charge of incoming electrons, Sugiyama’s semi-empirical formula is embedded in the formula. An analytical expression for the practical SP calculations using Bethe approximation and Thomas-Fermi model of atom is taken from an pervious study and the calculated results of the SPs from this formula for electrons in some elemental solids, such as Al, Si, Cr, Ni, Cu, Ge, Pd, Ag, Pt, and Au, are calculated and rigorously compared with experimental data, Penelope code results and with results of other calculations such as the non-relativistic Bethe SP equation and the empirical modification of the Bethe equation by Joy and Luo. The results are found to be in good agreement for some targets but some limited agreement for some energies and targets is also observed.     

Evaluations of structural,thermal, spectral,and magnetic properties of Li0.5Fe2.5O4 multi magnetic oxide fabricated via sol-gel auto-ignition technique

In³⁺ incorporated lithium ferrites have been synthesized via sol-gel auto-ignition route, and these were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometer (VSM). Thermal analysis of pure sample shows 12% weight loss in three successive steps observed by Thermogravimetric analysis (TGA). The lattice constant, cell volume, radii (R_t and R_o), and hopping lengths exhibited decreasing behavior, while crystallite size, X-ray, and bulk densities show an increasing trend with indium substitution. The bond length of each side decreases as indium content increases. The squareness ratio (R) exhibited that synthesized ferrites are single domain. The moderate value of saturation magnetization with a small H_c and squareness ratio proposed that synthesized ferrites may be suitable for high-frequency applications.     

掺杂少量Sm时La0.67-xSmxSr0.33MnO3(0.00≤x≤0.30)的磁电性质

通过测量样品的磁化强度-温度(M-T)曲线、电阻率-温度(ρ-T)曲线及磁电阻(magnetoresistance)-温度(MR-T)曲线,研究了Sm掺杂(x=0.00,0.10,0.20,0.30)对La0.67-xSrmxSr0.33MnO3磁电性质的影响.发现在铁磁相主要是单磁子散射起作用,表现为金属型导电,可用公式ρ=ρ0+AT2拟合,其中ρ为温度T时的电阻率;ρ0为0 K时的电阻率;A为常数.顺磁相的输运机制主要是小极化子跃迁起作用,可以用公式ρ=BTexp·(Ea/kBT)拟合,其中Ea为激活能;kB为Bolzman常数;B为常数.在相变温区是顺磁相的小极化子与铁磁相的单磁子2种输运性质共存.     

Preparation of Large Area Double Sided YBCO Thin Films by DC Magneton Sputtering

Tc, Jc and Rs properties of large area double sided YBCO thin films deposited on LaAlO3 substrates by direct current sputtering were reported.Film thickness of the obtained thin films is over 300 nm, Tc ＞ 90 K; Rs can be as low as less than 1.0 mΩ(77 K, 10 GHz).Homogenousity of the properties around the plane was studied.Under the measnous distributions.Influences of substrate temperature and Ar and O2 pressures on properties of the double-sided thin films were discussed.     

A review of the growth of V2O5 films from 1885 to 2010

This year is the 125th anniversary of the first synthesis of V₂O₅ gels. The fascinating properties and wide application range of V₂O₅ thin films have attracted significant attention over the past decades. Its wide optical band gap, layered structure, good chemical and thermal stability and excellent thermoelectric and electrochromic properties have made V₂O₅ a promising material for industrial applications such as gas sensors, electrochromic devices, optical switching devices, and reversible cathode materials for Li batteries. Gels were the first form in which V₂O₅ was synthesized at the end of the 19th century. Interest started to grow in the 1980s due to the discovery of their semiconducting properties and their use in antistatic coatings in the photographic industry. The rapid development of the sol-gel process brought new interest in V₂O₅ gels. Following a short discussion of vanadium oxides and V₂O₅, I summarize all thin film preparation techniques known up to now and use reported optical band gaps to characterize different growth methods. An estimation of the Bohr radius for V₂O₅ is also presented. This article provides an up-to-date review of more than a century (1885-2010) of research on the growth of vanadium oxide thin films. Nonetheless, due to the huge number of publications in the field, only those are selected and described which, according to the author, contribute the most to the field's further development.