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61.
T. Osada O. V. Utyuzh G. Wilk Z. Wodarczyk 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(1-2):7-10
The extended Gaussian ensemble introduced recently as a
generalization of the canonical ensemble, which allows to treat energy
fluctuations present in the system, is used to analyze the inelasticity
distributions in high energy multiparticle production processes. 相似文献
62.
D. Gao A. K. Ray 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(3):497-503
The electronic and geometrical properties of bulk americium and square and
hexagonal americium monolayers have been studied with the full-potential
linearized augmented plane wave (FP-LAPW) method. The effects of several
common approximations are examined: (1) non-spin polarization (NSP) vs. spin
polarization (SP); (2) scalar-relativity (no spin-orbit coupling (NSO)) vs.
full-relativity (i.e., with spin-orbit (SO) coupling included); (3)
local-density approximation (LDA) vs. generalized-gradient approximation
(GGA). Our results indicate that both spin polarization and spin orbit
coupling play important roles in determining the geometrical and electronic
properties of americium bulk and monolayers. A compression of both americium
square and hexagonal monolayers compared to the americium bulk is also
observed. In general, the LDA is found to underestimate the equilibrium
lattice constant and give a larger total energy compared to the GGA
calculations. While spin orbit coupling shows a similar effect on both
square and hexagonal monolayer calculations regardless of the model, GGA
versus LDA, an unusual spin polarization effect on both square and hexagonal
monolayers is found in the LDA results as compared with the GGA results. The
5f delocalization transition of americium is employed to explain our observed
unusual spin polarization effect. In addition, our results at the LDA level
of theory indicate a possible 5f delocalization could happen in the americium
surface within the same Am II (fcc crystal structure) phase, unlike the
usually reported americium 5f delocalization which is associated with crystal
structure change. The similarities and dissimilarities between the
properties of an Am monolayer and a Pu monolayer are discussed in detail. 相似文献
63.
CoFe alloy thin films were studied with the intention of potential use as a soft underlayer (SUL) for Co-based perpendicular recording media. The effect of composition and the effects of seedlayers on the formation of crystalline phase and crystallographic texture and the magnetic properties were investigated. Films deposited on Ta/Pd seedlayer were found to have a good FCC(1 1 1) texture than those deposited on glass substrates or on Ta seedlayers. The magnetic properties were also better when deposited on Ta/Pd seedlayers. On these seedlayers, Fe concentration of 15 at% was found to be suitable for the formation of FCC phase. Disks were prepared with CoFe SULs. The noise of CoFe SUL is one of the challenges to be solved. 相似文献
64.
Proton nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation rates for the solid solution α-MnH0.06 have been measured over the temperature range 11-297 K and the resonance frequency range 20-90 MHz. A considerable shift and broadening of the proton NMR line and a sharp peak of the spin-lattice relaxation rate are observed near 130 K. These effects are attributed to the onset of antiferromagnetic ordering below the Néel temperature TN≈130 K. The proton NMR line does not disappear in the antiferromagnetic phase; this suggests a small magnitude of the local magnetic fields at H-sites in α-MnH0.06. The spin-lattice relaxation rate in the paramagnetic phase is dominated by the effects of spin fluctuations. 相似文献
65.
P.B FabritchnyiM.V Korolenko M.I AfanasovM Danot E Janod 《Solid State Communications》2003,125(6):341-346
Mössbauer parameters of 119Sn diamagnetic dopant cations in an antiferromagnetic compound having the ilmenite structure are for the first time reported. The spectra reveal a well resolved hyperfine splitting pattern of combined magnetic and quadrupole interactions (at 5 K, δ=0.19 mm/s, H1=52.5 kOe, eVZZQ3/2=−0.80 mm/s, θ≈0°). This spectral component whose contribution (A1=82%) represents more than four fifths of the total amount of the dopant (Sn/(Mn+Ti)=1/200) is assigned to Sn(IV) ions located in the bulk of MnTiO3, on the Mn(II) site, and with a Mn(II) vacancy in their nearest surrounding. Two spectral components with minor contributions are also observed: one of them (H2≈25 kOe, A2=8%) can be assigned to Sn(IV) ions, in the MnTiO3 lattice as well, on a site where they exhibit a weaker spin polarization (this site could be the Ti(IV) one) and the other (H3=0 kOe, A3=10%) to SnO2 or/and Ti1−xSnxO2 clusters. The Néel temperature of MnTiO3 probed by the 119Sn dopant (TN=69±2 K) agrees well with the values previously provided by ESR and antiferromagnetic resonance measurements. Variation of H1 with temperature follows close the Brillouin function for S=5/2. No perturbation appears in the Mössbauer spectra around T=90 K where a broad peak, characteristic of 2D magnetic interactions, is observed on the static magnetic susceptibility curve. 相似文献
66.
W. Apel H.-U. Everts U. Körner 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):317-324
A coherent state representation for the electrons of ordered antiferromagnets is used to derive effective Hamiltonians for
the dynamics of holes in such systems. By an appropriate choice of these states, the constraint of forbidden double occupancy
can be implemented rigorously. Using these coherent states, one arrives at a path integral representation of the partition
function of the systems, from which the effective Hamiltonians can be read off. We apply this method to the t-J model on the square lattice and on the triangular lattice. In the former case, we reproduce the well-known fermion-boson
Hamiltonian for a hole in a collinear antiferromagnet. We demonstrate that our method also works for non-collinear antiferromagnets
by calculating the spectrum of a hole in the triangular antiferromagnet in the self-consistent Born approximation and by comparing
it with numerically exact results.
Received: 23 December 1997 / Accepted: 17 March 1998 相似文献
67.
T. Rudolf Ch. Kant F. Mayr M. Schmidt V. Tsurkan J. Deisenhofer A. Loidl 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(2):153-160
We studied the optical properties of antiferromagnetic ZnCr2Se4 by infrared spectroscopy up to 28,000 cm-1 and for temperatures from 5 to 295 K. At the magnetic phase transition at 21 K, one of the four phonon modes reveals a clear
splitting of 3 cm-1 as a result of spin-phonon coupling, the other three optical eigenmodes only show shifts of the eigenfrequencies. The antiferromagnetic
ordering and the concomitant splitting of the phonon mode can be suppressed in a magnetic field of 7 T. At higher energies
we observed a broad excitation band which is dominated by a two-peak-structure at about 18,000 cm-1 and 22,000 cm-1, respectively. These energies are in good agreement with the expected spin-allowed crystal-field transitions of the Cr3+ ions. The unexpected strength of these transitions with d-d character is attributed to a considerable hybridization of the
selenium p with the chromium d orbitals. 相似文献
68.
V.I. Nizhankovskii A.I. Khar'kovskii A.J. Zaleski 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(4):761-766
Spontaneous magnetisation of (100) and (010) surfaces of single crystal MnF2 in the antiferromagnetic state has been discovered. The sign of the surface magnetisation is determined by the difference
in dielectric constants of MnF2 and ambient matter: magnetisation is directed to the substance with smaller .
Received 28 August 1998 and Received in final form 15 December 1998 相似文献
69.
P.D. Hatton R.D. Johnson C. Mazzoli C.-H. Du 《Journal of magnetism and magnetic materials》2009,321(7):810-813
Full polarisation analysis of resonant X-ray magnetic scattering (RXMS) is shown to advance the determination of magnetic moment directions of complex magnetic structures within single crystals. Key features of this novel method are the variation of the incident beam polarisation through the use of an X-ray phase plate, and the measurement of the scattered beam polarisation in terms of Poincaré-Stokes parameters. Contrary to the established method, no azimuthal rotation is required. Thus, the major sources of systematic error are eliminated, and the method is compatible with exotic and complex sample environments. The technique is demonstrated with the example of TbMn2O5. The RXMS theory briefly outlined in this paper was fitted to the data, and the local and delocalized, band-specific moment directions associated with the magnetic order of the resonating species was refined with a high degree of accuracy. 相似文献
70.
Tumor growth has long been a target of investigation within the context of mathematical and computer modeling. The objective of this study is to propose and analyze a two-dimensional stochastic cellular automata model to describe avascular solid tumor growth, taking into account both the competition between cancer cells and normal cells for nutrients and/or space and a time-dependent proliferation of cancer cells. Gompertzian growth, characteristic of some tumors, is described and some of the features of the time-spatial pattern of solid tumors, such as compact morphology with irregular borders, are captured. The parameter space is studied in order to analyze the occurrence of necrosis and the response to therapy. Our findings suggest that transitions exist between necrotic and non-necrotic phases (no-therapy cases), and between the states of cure and non-cure (therapy cases). To analyze cure, the control and order parameters are, respectively, the highest probability of cancer cell proliferation and the probability of the therapeutic effect on cancer cells. With respect to patterns, it is possible to observe the inner necrotic core and the effect of the therapy destroying the tumor from its outer borders inwards. 相似文献