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White DB Tippens WB Abegg R Baldisseri A Boudard A Briscoe W Fabbro B Garçon M Hermes EA Jacobs WW Kessler RS Lytkin L Mayer B Nefkens BM Niebuhr C Petrov AM Poitou J Saudinos J Tomasi-Gustafsson E van der Schaaf A van Oers WT Vigdor SE Wang M 《Physical review D: Particles and fields》1996,53(11):6658-6661
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M. Pinterić M. Miljak N. Biškup O. Milat I. Aviani S. Tomić D. Schweitzer W. Strunz I. Heinen 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(2):217-225
We report a detailed characterization of the magnetism and AC transport in single crystals of the organic conductor -(BEDT-TTF)2Cu[N(CN)2]Cl by means of magnetic anisotropy measurements and low-frequency dielectric spectroscopy. Magnetic anisotropy obeys Curie-Weiss
law with negative Curie-Weiss temperature in the temperature range 300 K-70 K. An antiferromagnetic transition with concomitant
canted antiferromagnetic state is established at 22 K. A large hysteresis in the spin-flop transition and magnetic field reversal
of the weak ferromagnetic magnetization are documented for the first time. A broad dielectric relaxation mode of moderate
strength () emerges at 32 K, and weakens with temperature. The mean relaxation time, much larger than that expected for single-particle
excitations, is thermally activated in a manner similar to the DC conductivity and saturates below 22 K. These features suggest
the origin of the broad relaxation as an intrinsic property of the weak ferromagnetic ground state. We propose a charged domain
wall in a random ferromagnetic domain structure as the relaxation entity. We argue that the observed features might be well
described if Dzyaloshinsky-Moriya interaction is taken into account. A Debye relaxation with similar temperature dependence
was also observed and seems to be related to an additional ferromagnetic-like, most probably, field-induced phase. We tentatively
associate this phase, whose tiny contribution was sample dependent, with a Cu2+ magnetic subsystem.
Received 15 June 1998 and Received in final form 1 February 1999 相似文献
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P. Strunz D. Mukherji G. Pigozzi R. Gilles T. Geue K. Pranzas 《Applied Physics A: Materials Science & Processing》2007,88(2):277-284
The Ni3Si-type nanoparticles dispersed in a mixture of H2O/D2O were characterised by SANS using the contrast variation method. The existence of a core-shell structure in the nanoparticles
with a Ni3Si(Al) core and amorphous SiOx shell is confirmed by the SANS measurements. The nanoparticles were produced by extracting precipitates from a bulk Ni-13.3Si-2Al
( at. %) alloy using electrochemical phase separation technique and were pre-characterised by X-ray diffraction and transmission
electron microscopy. By comparing the precipitate morphology in the Ni-Si-Al alloy with the extracted nanoparticles in the
SANS measurements, it is clearly established that the precipitates shape and size are unaffected by the extraction process
and that the amorphous shell forms on top of the particle core. However, the present measurement could not confirm or exclude
the presence of H atoms in the shell structure.
PACS 61.12.Ex; 61.12.-q; 61.46.Df; 61.82.Rx 相似文献
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Grüner B Schlesinger M Heister P Strunz WT Stienkemeier F Mudrich M 《Physical chemistry chemical physics : PCCP》2011,13(15):6816-6826
The vibrational wave-packet dynamics of diatomic rubidium molecules (Rb(2)) in triplet states formed on the surface of superfluid helium nanodroplets is investigated both experimentally and theoretically. Detailed comparison of experimental femtosecond pump-probe spectra with dissipative quantum dynamics simulations reveals that vibrational relaxation is the main source of dephasing. The rate constant for vibrational relaxation in the first excited triplet state 1(3)Σ(g)+ is found to be constant γ ≈ 0.5 ns(-1) for the lowest vibrational levels v ? 15 and to increase sharply when exciting to higher energies. 相似文献
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R. Beck M. Gradzielski K. Horbaschek S. S. Shah H. Hoffmann P. Strunz 《Colloid and polymer science》2000,278(2):137-142
The phase behaviour and properties of the tetradecyldimethylamine oxide/HCl/hexanol/water quaternary surfactant system have
been studied by means of electric conductivity, rheology, freeze-fracture transmission electron microscopy (FF-TEM) and small-angle
neutron scattering (SANS). In this system the originally zwitterionic surfactant can become increasingly charged by protonation
through the addition of HCl, i.e. the degree of charging can be changed continuously. An interesting, isotropic phase (L1
* phase) of low viscosity was observed for intermediate degrees of charging. From viscosity and conductivity measurements this
phase can clearly be distinguished from the conventional L1 phase that is composed of micelles. Investigation of the structures present by means of FF-TEM and SANS showed that the L1
* phase is made up of unilamellar vesicles of extremely small diameter of 8–10 nm. Evidently such highly curved structures
are stabilized by the electrostatic conditions in this system.
Received: 11 July 1999/Accepted: 25 August 1999 相似文献
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During the investigation of the reaction of dichloroketene with cyclic enoxy-lactones and acyclic enoxy-ester substrates it was found that only the acylic variants effectively participated in the [2+2]-cycloaddition. Although a complete understanding of the reasons for this are lacking, molecular mechanics calculations do suggest that an out of plane twist of the cabonyl group in the acyclic compounds may be partially responsible. After screening a variety of chiral auxiliaries it was found that useful levels of diastereoselectivity (2.6-10.8:1) could be obtained in this cycloaddition reaction when (R)-2,2-diphenylcyclopentanol was used as the chiral auxiliary. 相似文献
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Heerklotz H Tsamaloukas A Kita-Tokarczyk K Strunz P Gutberlet T 《Journal of the American Chemical Society》2004,126(50):16544-16552
The thermotropic sphere-to-rod transition of nonionic surfactants was characterized in terms of a large set of parameters: the transition temperature and width, the partial volume, coefficient of thermal volume expansion, enthalpy, isobaric heat capacity, and structural parameters, such as radius of gyration and hydrodynamic radius. Data were recorded as a function of concentration of surfactants in H2O and in D2O. To this end, pressure perturbation calorimetry (PPC), small angle neutron scattering (SANS), dynamic light scattering (DLS), differential scanning calorimetry (DSC), and isothermal titration calorimetry (ITC) were applied in a study of aqueous solutions containing myristyl, tridecyl, and lauryl maltoside and heptaethyleneglycoltetradecyl ether (C14EO7). Small changes in the thermodynamic and volumetric parameters (e.g., the partial volume change is approximately +2 per thousand) are discussed in detail as the result of three effects governing the transition. (i) Reduction of the water accessible hydrophobic surface area (ASA(ap)) drives the transition. (ii) Shrinking in headgroup size by thermal dehydration triggers the transition. (iii) Hypothesized gradual ordering of the chains may control the effect of chain length on the transition. 相似文献