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1.
Examination of the ground-state correlation properties of two Coulombically interacting bosons confined in strongly anisotropic harmonic potentials is carried out within the framework of the single-mode approximation of the transverse components. The linear entropy of the quasi-one dimensional systems is discussed in dependence on the confinement anisotropy and the interaction strength. A comparison with a strictly one-dimensional limit is performed. 相似文献
2.
N. Vukadinovic M. Labrune J. Ben Youssef 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(4):593-602
Within the framework of two-dimensional (2D) numerical micromagnetic simulations, the equilibrium magnetization configuration
and the high-frequency (0.1–30 GHz) linear response of Co/Fe multilayers have been investigated in detail. Due to the perpendicular
anisotropy of Co layers, a stripe domain pattern can develop through the whole multilayer, the characteristics of which depend
on the magnitude of the perpendicular anisotropy, the respective thicknesses of Co and Fe layers and the number of Co/Fe bilayers
in the stack. One of the most striking features associated with the layering effect is the ripening aspect of the static magnetization
configuration across the multilayers which induces complicated dynamic susceptibility spectra including surface modes and
volume modes strongly confined within the inner Fe layers. The effect of the cubic magnetocrystalline anisotropy of Fe layers
and the influence of a nonuniform perpendicular magnetic anisotropy within the Co layers on the static and dynamic magnetic
properties of Co/Fe multilayers are then analyzed quantitatively. 相似文献
3.
On the use of 2D correlation and exchange NMR spectroscopy in organic porous materials 总被引:1,自引:0,他引:1
Two-dimensional (2D) nuclear magnetic resonance (NMR) methods for the investigation of correlation and exchange have been introduced in recent years and have been applied to a range of different systems. Here, we report on the use of 2D NMR diffusion-diffusion correlation spectroscopy for the investigation of diffusion anisotropy in cellular plant tissues and of diffusion-diffusion exchange spectroscopy for the study of the diffusive exchange of dextran in a dispersion of polyelectrolyte multilayer hollow capsules. Furthermore, diffusion-relaxation correlation spectroscopy was applied to both systems. 相似文献
4.
The thermodynamic properties of anisotropic quasiparticle systems of He II are considered for all degrees of anisotropy. It is shown that the thermodynamic functions of a strongly anisotropic phonon-roton system are mainly determined by rotons at all temperatures. Analytical expressions for the roton thermodynamic functions are obtained for all degrees of anisotropy. The maximum anisotropy is limited by the criterion for thermodynamic stability, which is here derived for the whole temperature range. 相似文献
5.
We present a simulation of the magnetization curves, energy, probability, and torque landscapes of uniaxial systems with up to five anisotropy constants. The total energy used in the simulation is the sum of the anisotropy and Zeeman energies. The exchange interaction is not considered in the present work in which we treat single-domain-particle systems within a classical mechanics-based model. Diverse features of the calculated magnetization curves are highlighted for the studied systems. These diverse features are strongly dependent on the sign and magnitude of the simulation parameters.The model is versatile enough to handle both hypothetical and real material systems, e.g. HoFe_(11)Ti and Y_2Co_(17). 相似文献
6.
Gambardella P Dallmeyer A Maiti K Malagoli MC Rusponi S Ohresser P Eberhardt W Carbone C Kern K 《Physical review letters》2004,93(7):077203
One-dimensional Co atomic wires grown on Pt(997) have been investigated by x-ray magnetic circular dichroism. Strong changes of the magnetic properties are observed as the system evolves from 1D- to 2D-like. The easy axis of magnetization, the magnetic anisotropy energy, and the coercive field oscillate as a function of the transverse width of the wires, in agreement with theoretical predictions for 1D metal systems. 相似文献
7.
We introduce a variational method for the approximation of ground states of strongly interacting spin systems in arbitrary geometries and spatial dimensions. The approach is based on weighted graph states and superpositions thereof. These states allow for the efficient computation of all local observables (e.g., energy) and include states with diverging correlation length and unbounded multiparticle entanglement. As a demonstration, we apply our approach to the Ising model on 1D, 2D, and 3D square lattices. We also present generalizations to higher spins and continuous-variable systems, which allows for the investigation of lattice field theories. 相似文献
8.
We present a numerical method to evaluate partition functions and associated correlation functions of inhomogeneous 2D classical spin systems and 1D quantum spin systems. The method is scalable and has a controlled error. We illustrate the algorithm by calculating the finite-temperature properties of bosonic particles in 1D optical lattices, as realized in current experiments. 相似文献
9.
The small-size partially filled one-dimensional (1D) lattice gas system with
1/rδ repulsive interactions is numerically studied. Our results
indicate that phase change with vacancy ordering involved exists in the
partially filled 1D lattice gas systems, and the phase properties of the
studied system strongly depend on the occupancy nav and the interaction
strength δ. Most interestingly, it is found that the phase change
still exists in the 1D finite-size lattice gas systems even with nearest
neighbor interactions, i.e. δ is infinite. These results provide
valuable information about the phase properties of 1D confined systems, such
as molecules inside the carbon nanotubes, with long-range interactions
between particles. 相似文献
10.
We study a model of strongly correlated fermions in one dimension with extended N = 2 supersymmetry. The model is related to the spin S = 1/2 XXZ Heisenberg chain at anisotropy Delta = -1/2 with a real magnetic field on the boundary. We exploit the combinatorial properties of the ground state to determine its exact wave function on finite lattices with up to 30 sites. We compute several correlation functions of the fermionic and spin fields. We discuss the continuum limit by constructing lattice observables with well defined finite-size scaling behavior. For the fermionic model with periodic boundary conditions we give the emptiness formation probability in closed form. 相似文献
11.
A quasi-two-dimensional ferromagnet (S = 1) with easy axis type anisotropy and interplanar exchange J and intraplanar exchange K is examined within the framework of the spin-wave approximation. An expression for the Curie temperature that is dependent on both the anisotropy parameter D (D/J 1) and on the exchange parameter ratio =K/J is obtained from the self-consistent equations. The important role of the single-ion anisotropy in the formation of the long-range magnetic order in two-dimensional systems is shown.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 94–101, March, 1988.The authors are grateful to S. S. Aplesnin for performing all the numerical computations and to I. S. Sandalov and A. F. Sadreev for useful discussions. 相似文献
12.
Tacchi S Gr?n?s O Stollo A Madami M Gubbiotti G Carlotti G Marangolo M Eddrief M Etgens VH Yadav MK Nordstr?m L Sanyal B 《J Phys Condens Matter》2012,24(23):236006
It is well known that Fe films deposited on a c(2 × 2)-reconstructed ZnSe(001) surface show a strong in-plane uniaxial magnetic anisotropy. Here, the effect of the substrate reconstruction on the magnetic anisotropy of Fe has been studied by in situ Brillouin light scattering. We found that the in-plane uniaxial anisotropy is strongly reduced for Fe films grown on a (1 × 1)-unreconstructed ZnSe substrate while the in-plane biaxial one is nearly unaffected by the substrate reconstruction. Calculations of magnetic anisotropy energies within the framework of ab initio density functional theory reveal that the strong suppression of anisotropy at the (1 × 1) interface occurs due to complex atomic relaxations as well as the competing effects originating from magnetocrystalline anisotropy and dipole-dipole interactions. For both sharp and intermixed c(2 × 2) interfaces, the magnetic anisotropy is enhanced compared to the (1 × 1) case due to the further lowering of symmetry. The theoretical results are in agreement with the experimental findings. 相似文献
13.
Recent experiments on iron pnictides have uncovered a large in-plane resistivity anisotropy with a surprising result: The system conducts better in the antiferromagnetic x direction than in the ferromagnetic y direction. We address this problem by calculating the ratio of the Drude weight along the x and y directions, D(x)/D(y), for the mean-field Q=(π,0) magnetic phase diagram of a five-band model for the undoped pnictides. We find that D(x)/D(y) ranges between 0.2相似文献
14.
Values for the random anisotropy (D) and exchange (J) constants in amorphous DyxGd1?xNi have been obtained from an analysis of the measured magnetization curves in terms of the H.P.Z. model. Within the molecular field approximation this model is suitable in high magnetic fields. In low fields, other properties, characteristic of random anisotropy systems, arise which are not taken into account in this model. 相似文献
15.
Equilibrium state and magnetic excitations are studied within a phenomenological model for disordered magnetic systems with ferromagnetic exchange and weak random anisotropies. These systems exhibit the new type of magnetic behaviour characterized by finite ferromagnetic correlation length at zero temperature. Effects of coherent anisotropy and external magnetic field are considered. 相似文献
16.
Laburthe Tolra B O'Hara KM Huckans JH Phillips WD Rolston SL Porto JV 《Physical review letters》2004,92(19):190401
We investigate the correlation properties of a one-dimensional interacting Bose gas by loading a magnetically trapped 87Rb Bose-Einstein condensate (BEC) into a deep two-dimensional optical lattice. We measure the three-body recombination rate for both the BEC in the magnetic trap and the BEC loaded into the optical lattice. The recombination rate coefficient is a factor of 7 smaller in the lattice, which we interpret as a reduction in the local three-body correlation function in the 1D case. This is a signature of correlation intermediate between that of the uncorrelated, phase coherent, 1D, mean-field regime and the strongly correlated Tonks-Girardeau regime. 相似文献
17.
C. L. Lu C. P. Chang M. F. Lin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(2):161-169
In this study, we apply the tight-binding method to
magneto-electronic properties of the AA- and ABC-stacked graphites,
which are strongly dependent on the interlayer interactions, the
magnetic field, and the stacking sequences. First of all, the
interlayer interactions induce the significant changes in the energy
dispersions, the band symmetry about the Fermi level, the overlap
between valence and conduction bands, the band width, and the
band-edge states or the symmetry points. Then, the magnetic field
induces the Peierls phase in the Bloch functions and thus strongly
affects the energy dispersions of the Landau Levels, the subband
spacings, the energy width, and the special structures in density of
states (DOS). Finally, the stacking sequences dominates over the
low-energy band overlap and the anisotropy of energy bands. The
effects mentioned above are exactly reflected in the density of
state. Here, DOS exhibits the 3D, 2D, and 1D characteristics. 相似文献
18.
R.
uberek K. Fronc A. Szewczyk H. Szymczak 《Journal of magnetism and magnetic materials》2003,260(3):386-392
The magnetic anisotropy and magnetoelastic properties of epitaxial iron films prepared by DC magnetron sputtering on single crystal GaAs(0 0 1) substrate and covered with a protective Si or Ge layer have been investigated by means of the ferromagnetic resonance and strain-modulated ferromagnetic resonance. It has been shown that the uniaxial and cubic anisotropy constants as well as two magnetoelastic constants strongly depend on the thickness of the film. The surface components of the cubic anisotropy and magnetoelastic constants have been determined. 相似文献
19.
Three-and two-dimensional calculations for the interface anisotropy dependence of magnetic properties of exchange-spring Nd2Fe(14)B/α-Fe multilayers with out-of-plane easy axes 下载免费PDF全文
Hysteresis loops,energy products and magnetic moment distributions of perpendicularly oriented Nd2Fe(14)B/α-Fe exchange-spring multilayers are studied systematically based on both three-dimensional(3D)and one-dimensional(1D)micromagnetic methods,focused on the influence of the interface anisotropy.The calculated results are carefully compared with each other.The interface anisotropy effect is very palpable on the nucleation,pinning and coercive fields when the soft layer is very thin.However,as the soft layer thickness increases,the pinning and coercive fields are almost unchanged with the increment of interface anisotropy though the nucleation field still monotonically rises.Negative interface anisotropy decreases the maximum energy products and increases slightly the angles between the magnetization and applied field.The magnetic moment distributions in the thickness direction at various applied fields demonstrate a progress of three-step magnetic reversal,i.e.,nucleation,evolution and irreversible motion of the domain wall.The above results calculated by two models are in good agreement with each other.Moreover,the in-plane magnetic moment orientations based on two models are different.The 3D calculation shows a progress of generation and disappearance of vortex state,however,the magnetization orientations within the film plane calculated by the 1D model are coherent.Simulation results suggest that negative interface anisotropy is necessarily avoided experimentally. 相似文献
20.
We report the femtosecond dynamics of fluorescence anisotropy excited through the two-photon absorption (TPA), which provides direct signatures of delocalized electronic excitations for symmetrical macromolecular architectures. Two-photon excited fluorescence anisotropy is strongly correlated with the orientation and value of the transition moment from the excited state to the second and higher lying states. For macromolecular systems it leads to a relatively low initial fluorescence anisotropy and specific femtosecond anisotropy dynamics. We have experimentally demonstrated qualitatively different anisotropy dynamics for two- and one-photon absorption excitations for strongly coupled ring architecture prospective for artificial-light-harvesting applications and possessing an enhanced TPA-absorption cross section. 相似文献