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141.
142.
Boothroyd AT Coldea R Tennant DA Prabhakaran D Helme LM Frost CD 《Physical review letters》2004,92(19):197201
We present neutron scattering spectra taken from a single crystal of Na0.75CoO2, the precursor to a novel cobalt-oxide superconductor. The data contain a prominent inelastic signal at low energies ( approximately 10 meV), which is localized in wave vector about the origin of two-dimensional reciprocal space. The signal is highly dispersive, and decreases in intensity with increasing temperature. We interpret these observations as direct evidence for the existence of ferromagnetic spin fluctuations within the cobalt-oxygen layers. 相似文献
143.
Perception is influenced both by characteristics of the stimulus, and by the context in which it is presented. The relative contributions of each of these factors depend, to some extent, on perceiver characteristics. The contributions of word and sentence context to the perception of phonemes within words and words within sentences, respectively, have been well studied for normal, young adults. However, far less is known about these context effects for much younger and older listeners. In the present study, measures of these context effects were obtained from young children (ages 4 years 6 months to 6 years 6 months) and from older adults (over 62 years), and compared with those of the young adults in an earlier study [A. Boothroyd and S. Nittrouer, J. Acoust. Soc. Am. 84, 101-114 (1988)]. Both children and older adults demonstrated poorer overall recognition scores than did young adults. However, responses of children and older adults demonstrated similar context effects, with two exceptions: Children used the semantic constraints of sentences to a lesser extent than did young or older adults, and older adults used lexical constraints to a greater extent than either of the other two groups. 相似文献
144.
Boothroyd AT Freeman PG Prabhakaran D Hiess A Enderle M Kulda J Altorfer F 《Physical review letters》2003,91(25):257201
We have observed a diffuse component to the low-energy magnetic excitation spectrum of stripe-ordered La(5/3)Sr(1/3)NiO4 probed by neutron inelastic scattering. The diffuse scattering forms a square pattern with sides parallel and perpendicular to the stripe directions. The signal is dispersive, with a maximum energy of approximately 10 meV. Probed at 2 meV, the scattering decreases in strength with increasing temperature, and is barely visible at 100 K. We argue that the signal originates from dynamic, quasi-one-dimensional, antiferromagnetic correlations among the stripe electrons. 相似文献
145.
Wilkins SB Hatton PD Roper MD Prabhakaran D Boothroyd AT 《Physical review letters》2003,90(18):187201
We have conducted the first soft x-ray diffraction experiments from a bulk single crystal, studying the bilayer manganite La2-2xSr1+2xMn2O7 with x=0.475 in which we were able to access the (002) Bragg reflection using soft x rays. The Bragg reflection displays a strong resonant enhancement at the L(III) and L(II) manganese absorption edges. We demonstrate that the resonant enhancement of the magnetic diffraction of the (001) is extremely large, indeed so large that it exceeds that of the nonresonant Bragg diffraction. Resonant soft x-ray scattering of 3d transition metal oxides is the only technique for the atomic selective measurement of spin, charge, and orbital correlations in materials, such as high temperature superconductors, colossal magnetoresistance manganites, and charge stripe nickelates. 相似文献
146.
R.L.D. Whitby W.K. Hsu C.B. Boothroyd K.S. Brigatti H.W. Kroto D.R.M. Walton 《Applied Physics A: Materials Science & Processing》2003,76(4):527-532
Time-dependent powder X-ray-diffraction analyses reveal that the conversion of WO3 into WS2 on carbon nanotube surfaces in the presence of H2S is a one-step process. The WS2 layers grow simultaneously along the tube in the radial and axial directions.
Received: 17 June 2002 / Accepted: 19 June 2002 / Published online: 15 January 2003
RID="*"
ID="*"Corresponding author. Fax: +44-1273/677-196, E-mail: d.walton@sussex.ac.uk 相似文献
147.
148.
Boothroyd AT Gardiner CH Lister SJ Santini P Rainford BD Noailles LD Currie DB Eccleston RS Bewley RI 《Physical review letters》2001,86(10):2082-2085
Neutron spectroscopic measurements of the magnetic excitations in PrO2 reveal (1) sharp peaks characteristic of transitions between levels of the 4f(1) configuration of Pr4+ split by the cubic crystal field, and (2) broad bands of scattering centered near 30 and 160 meV. We present a simple model based on a vibronic Hamiltonian that accounts for these contrasting features of the data. The analysis shows that 90%+/-10% of the Pr ions have a localized 4f(1) configuration and provides strong evidence for a dynamic Jahn-Teller effect in the gamma(8) electronic ground state. 相似文献