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排序方式: 共有188条查询结果,搜索用时 15 毫秒
91.
Seiji Sakai Seiji Mitani Yoshihiro Matsumoto Shiro Entani Pavel Avramov Manabu Ohtomo Hiroshi Naramoto Koki Takanashi 《Journal of magnetism and magnetic materials》2012
Voltage-dependence of the tunneling magnetoresistance effect in the granular C60–Co films has been investigated for the samples with the current-perpendicular-to-plane geometry. The transport measurements under this geometry demonstrate that the granular C60–Co films show an unusual exponential bias voltage dependence of the magnetoresistance ratio down to zero voltage. Small characteristic energies of less than 10's meV are derived from the temperature dependences of the characteristic voltage in the exponential relationship. Considering the magnitudes of the voltage drop between Co nanoparticles and also the effect of cotunneling on the energy values, the characteristic energies for the voltage-induced degradation of the spin polarization are found to show a satisfactory agreement with that for the thermally-induced one. It can be reasonably expected that the onset of magnetic disorder to the localized d-electron spins at the interface region of the C60-based matrix (C60–Co compound) with Co nanoparticles leading to the unusual voltage and temperature dependence of the magnetoresistance ratio and the spin polarization at low temperatures. 相似文献
92.
We shall present a couple of norm inequalities which will much improve the sharp triangle inequality with n elements and its reverse inequality in a Banach space shown recently by the last three authors. 相似文献
93.
Fukuji Higashi Takayo Shirai Kiyoshi Mitani Kanako Sugishita 《Journal of polymer science. Part A, Polymer chemistry》2001,39(22):3884-3892
A mixture of isophthalic acid (IPA) and terephthalic acid (TPA) was activated by a tosyl chloride/dimethylformamide/pyridine (Py) condensing agent in two steps via the treatment of a mixture of the initially activated IPA/TPA with additional TPA followed by the activation of TPA with the agent. The resulting mixture showed a solubility in Py different from that obtained by the activation of them all at once; the difference might be due to different structures of the aggregates of the activated IPA and TPA at the same composition of the diacids. The structures of the aggregates were evaluated on the basis of melting points and the IR spectra of a mixture of dimethyl esters of IPA and TPA produced by the quenching of the reaction mixtures with methanol. The mixture obtained by two‐step activation showed lower melting points and spectral changes due to enhanced associations of the esters with respect to the mixture prepared by the activation of them all at once. The aggregates were also examined in terms of the distributions of IPA and TPA in thermotropic copolyesters prepared from methylhydroquinone and chlorohydroquinone by their transition temperatures and 13C NMR. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3884–3892, 2001 相似文献
94.
Katsuo Mitani Takayuki Ogata Michio Nakatsukasa Hiroshi Awaya Yasuo Tomari 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(4):531-549
The mechanism of vinyl chloride polymerization by the tri-ethylaluminum-Lewis base-carbon tetrachloride catalyst system and the thermal stability of the resulting polymer were investigated. When the Lewis base is multidentate, the resultant complex with triethylaluminum shows significantly high catalytic activity for radical polymerization of vinyl chloride in the presence of carbon tetrachloride to give a white powder with high molecular weight. Carbon tetrachloride accelerates the rate of polymerization and participates in an initiating process rather than in a propagating step. The thermal stability of the polymer prepared with this catalyst system is much superior to that of commercial polyvinyl chloride), although the numbers of the double bonds in a chain end and of the head-to-head linkage are similar in both samples, suggesting that the thermally unstable structures of the former react with triethylaluminum to give the thermally stable structure on the polymerization process. 相似文献
95.
96.
Fukuji Higashi Kiyoshi Mitani 《Journal of polymer science. Part A, Polymer chemistry》1999,37(19):3710-3714
When mixtures of terephthalic acid (TPA) and 1,6-naphthalenedicarboxylic acid (NDC) or 4,4′-dicarboxydiphenylether (DCDPE), TPA, and isophthalic acid (IPA) were reacted in pyridine (Py) with Tosyl chloride (TsCl)/DMF/Py to activate the diacids, the reaction mixture was soluble in Py, despite each of the separately activated diacids being insoluble. The solubility of the activated diacids was examined at a variety of acid compositions and temperatures. It was expected that a competitive reaction among the diacids with an aromatic diol in solution might be different from those in the melt, resulting in a different distribution of the acids in the copolymers. The TPA/NDC-phenylhydroquinone and DCDPE/TPA/IPA-chlorohydroquinone copolymers were prepared in solution using TsCl/DMF/Py as the condensing agent and the transition temperatures of these liquid crystalline copolyesters were compared to those obtained by melt copolycondensation. A practical depression of the transition temperature by the solution polycondensation was observed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3710–3714, 1999 相似文献
97.
Mitsumi M Yamashita T Aiga Y Toriumi K Kitagawa H Mitani T Kurmoo M 《Inorganic chemistry》2011,50(10):4368-4377
We present a comprehensive study of the temperature dependence of the crystal structure using single-crystal X-ray diffraction and diffuse scattering, and electrical transport and magnetic properties as well as some optical properties at room temperature to elucidate the origin and the form of multiple ground states demonstrated in a previous study of the heat-capacity of the MMX chain compound, [Pt(II/III)(2)(n-PenCS(2))(4)I](∞). The present results confirm the presence of the two phase transitions, one reversible of first order at 207 K and the other nonreversible monotropic at 324 K, separating the low temperature (LT), room temperature (RT), and high temperature (HT) phases. The unit cell displays a 3-fold periodicity of -Pt-Pt-I- in the RT and HT phases because of the structural disorder which is exhibited by the dithiocarboxylato groups and the n-pentyl groups belonging to the central diplatinum unit. In addition, for the HT-phase all the dimers show this disorder. This compound undergoes a metal-semiconductor transition at T(M-S) = 235 K. The presence of diffuse streaks corresponding to 2-fold -Pt-Pt-I- periodicity in the HT and RT phases indicates dynamic valence ordering of the type -Pt(2+)-Pt(2+)-I(-)-Pt(3+)-Pt(3+)-I(-)-or-Pt(2+)-Pt(3+)-I(-)-Pt(3+)-Pt(2+)-I(-)-. For the LT-phase the diffuse scattering is condensed into clear Bragg diffraction peaks while keeping the 3-fold periodicity. This fact suggests further localization through dimerization of charges and spins confirming the diamagnetic state in the magnetic susceptibility and the low electrical conduction below 207 K. The present results are further discussed in relation to those of previous studies on the homologues, [Pt(II/III)(2)(RCS(2))(4)I](∞), R = methyl, ethyl, n-propyl, and n-butyl. 相似文献
98.
Mohd Sharizal Alias Sahbudin Shaari P. K. Choudhury Sufian Mitani 《Journal of Russian Laser Research》2009,30(4):368-375
A comprehensive study of the uniformity of 850 nm VCSEL epiwafer grown by the MOCVD technique is presented. By utilizing the
VCSEL planar structure, uniformity test is performed on-wafer directly, besides using the conventional photoluminescence technique.
The VCSEL quantum wells are found to exhibit a peak emission wavelength of 839.5 nm. Also, the grown epiwafer is observed
to exhibit a Fabry–Perot cavity resonance at 846.5 nm. Various VCSEL devices fabricated from the center to the edge of the
VCSEL epiwafer show a similar trend towards the light–current and output spectral characteristics. However, the device existing
near the epiwafer edge is observed to exhibit significantly different characteristics, which is attributed to the physical
conditions of the device near the edge, and also the limitations of the epitaxial growth. 相似文献
99.
H. Nagura K. Takanashi S. Mitani K. Saito T. Shima 《Journal of magnetism and magnetic materials》2002,240(1-3):183-185
Current-perpendicular-to-plane magnetoresistance was measured for ferrimagnetic Co/Gd multilayers which have twisted spin structure accompanied with spin-flop transition. The influence of twisted spin structure on the electronic transport was exclusively obtained, eliminating the effect of anisotropic magnetoresistance. MR curves showed a downturn around the spin-flop field, suggesting that the formation of twisted spin structure leads to a negative resistance change. 相似文献
100.
Polarized reflection spectra and their temperature-dependence as well are investigated on tetrathiafulvalene-p-chloranil (TTFCA) single crystals over the temperature range from 2 K to room temperature. Abrupt changes are observed at Tc = 84.4 ± 0.5 K in the charge transfer and intramolecular excitation bands. These experimental results strongly indicate that the dominant part of the neutral-to-ionic transition in this crystal takes place at a sharply defined critical temperature, in contrary to the recent observation by Torrance et al. [Phys. Rev. Lett.47, 1747 (1981)] that the transition occurs in a temperature range of about 30 K in width. A simple model is presented to account for the observed shift of the TTF+ intramolecular transition bands at Tc. 相似文献