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71.
High-resolution Fourier transform absorption and luminescence spectroscopy reveal axial and rhombic zero-field splittings of the spin-forbidden electronic origins of V3+ in NaMgAl(ox)3·9H2O (ox=oxalate) single crystals below 25 K. The temperature dependence of the integrated absorption of the split features display behavior consistent with a Boltzmann distribution within the zero-field split 3Â2 ground state of V3+. Weak luminescence is observed in the near-IR from the lowest energy spin-forbidden transition with a luminescence lifetime of less than 0.5 μs at 11 K and an estimated quantum efficiency of the order of 10−5. 相似文献
72.
V.Yu. Ivanov A.A. Mukhin V.D. Travkin A.S. Prokhorov A.M. Kadomtseva Yu.F. Popov G.P. Vorob’ev K.I. Kamilov A.M. Balbashov 《Journal of magnetism and magnetic materials》2006
Multiferroic ground states with a spatially modulated antiferromagnetic structure and electric polarization have been revealed in Eu1−xYxMnO3 (0.2?x?0.5) single crystals. While the slightly substituted (x?0.1) compounds exhibited a transition from the incommensurate (IC) to the canted antiferromagnetic (CAF) state at TCA<TN, the transitions from IC to commensurate ferroelectric (C/FE) phase were observed at Tlock<TN for x>0.2. Various phase transitions were observed in the magnetic fields up to 250 kOe along a, b, c axes by magnetization, magnetostriction and electric polarization measurements which show an existence of a spontaneous electric polarization below Tlock. 相似文献
73.
The magnetic domain structure of the Fe double-layer on W(1 1 0) is investigated using a variable-temperature scanning tunneling microscope. At low temperature the well-known periodic magnetic stripe domain structure is identified via the observation of domain walls. This is done with a non-spin-polarized tip by taking advantage of a spin–orbit coupling effect. At higher temperature a reorientation to an in-plane easy axis is observed. The spin reorientation temperature is found to be coverage-dependent and it is determined for samples with a coverage of 1.5–2.2 atomic layers of Fe on W(1 1 0). 相似文献
74.
75.
In this study, we have investigated the effect of substituting Mn for Fe on the crystallization kinetics of amorphous Fe73.5−xMnxCu1Nb3Si13.5B9 (x = 1, 3, 5, 7) alloys. The samples were annealed at 550 °C and 600 °C for 1 h under an argon atmosphere. The X-ray diffraction analyses showed only a crystalline peak belonging to the α-Fe(Si) phase, with the grain size ranging from 12.2 nm for x = 0 to 16.7 nm for x = 7. The activation energies of the alloys were calculated using Kissinger, Ozawa and Augis-Bennett models based on differential thermal analysis data. The Avrami exponent n was calculated from the Johnson-Mehl-Avrami equation. The activation energy increased up to x = 3, then decreased with increasing Mn content. The values of the Avrami exponent showed that the crystallization is typical diffusion-controlled three-dimensional growth at a constant nucleation rate. 相似文献
76.
D. Karevski Y-C. Lin H. Rieger N. Kawashima F. Iglói 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(2):267-276
We study the critical behavior of Ising quantum magnets with broadly distributed random couplings (J), such that P(ln J) ∼ | ln J|-1 - α, α > 1, for large | ln J| (Lévy flight statistics). For sufficiently broad distributions, α < , the critical behavior is controlled by a line of fixed points, where the critical exponents vary with the Lévy index, α.
In one dimension, with = 2, we obtained several exact results through a mapping to surviving Riemann walks. In two dimensions the varying critical
exponents have been calculated by a numerical implementation of the Ma-Dasgupta-Hu renormalization group method leading to
≈ 4.5. Thus in the region 2 < α < , where the central limit theorem holds for | ln J| the broadness of the distribution is relevant for the 2d quantum Ising model.
Received 6 December 2000 and Received in final form 22 January 2001 相似文献
77.
H. Hövel 《Applied Physics A: Materials Science & Processing》2001,72(3):295-302
With controlled growth in nanometer-sized pits we produced silver and gold clusters on a graphite surface. We give a summary
of the preparation method and discuss the scanning tunneling imaging and the crystalline orientation of the clusters. The
electronic structure of the clusters was studied by an in-situ combination of ultraviolet photoelectron spectroscopy (UPS)
and scanning tunneling spectroscopy (STS). For both techniques we obtained an energy resolution in the range of 10 meV employing
low sample temperatures. Dynamic final-state effects together with averaging over a cluster-size distribution result in characteristic
spectral shapes in UPS, which can be understood referring to STS data taken on individual clusters. Finally, directions for
future experiments are pointed out.
Received: 13 April 2000 / Accepted: 6 November 2000 / Published online: 9 February 2001 相似文献
78.
Reactively sputtered Ta-Si-Nx barrier systems of different nitrogen content on copper were investigated by photoelectron spectroscopy (XPS, UPS) and scanning tunnelling microscopy (STM). The measured photoelectron spectra (excitation He-I) showed a clear dependence of the electron state density near the Fermi edge on the content of nitrogen. These results correlate with the I(U) characteristics of the STM measurements and the electrical conductivity of these layers. 相似文献
79.
2 has been used for smoothing of rough InAs, InP, and InSb surfaces, prepared by argon ion beam etching (IBE). The evolution
of the surface roughness and morphology has been studied by atomic force microscopy (AFM) as a function of the N2 RIBE process parameters (ion beam energy, ion beam angle of incidence, and ion dose). A drastic improvement of the surface
roughness has been observed for ion beam angles near normal incidence and larger than 70° with increasing ion doses. By using
this technique, the initial root-mean-square (rms) roughness of, e.g., InSb of about 40 nm could be decreased to about 1 nm.
Received: 20 March 1998/Accepted: 24 March 1998 相似文献
80.
J. Boneberg M. Tresp M. Ochmann H.-J. Münzer P. Leiderer 《Applied Physics A: Materials Science & Processing》1998,66(6):615-619
2 ). This result demands a critical inspection of the interpretation of nanostructuring experiments with this technique.
Received: 15 August 1997/Accepted: 8 December 1997 相似文献