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1.
B.A. Hamad T. Khajil J.M. Khalifeh 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(3):497-501
The magnetism is calculated for substitutional alloyed of Crx(Mnx)V1-x monolayers (MLs) and CrxMn1-x on V (001) surface with a variety of concentrations (x
= 0.25, 0.50 and 0.75). The substitutional surface alloys were treated by an artificial super cell construction. Parallel magnetic
ordering is obtained for all the considered structures. The surface net magnetization increases in terms of Cr (Mn) concentration
in Crx(Mnx)V1-x/V (001) system, while no serious variations occur in CrxMn1-x/V (001). Vanadium atoms at the interfacial layers acquire appreciable magnetic moments antiferromagneticlly (AF) coupled
with the surface moments.
Received 25 February 2002 / Received in final form 13 May 2002 Published online 14 October 2002
RID="a"
ID="a"e-mail: jkalifa@sci.ju.edu.jo 相似文献
2.
F. Decker K.-P. Holzer P. Mischo J. Petersson D. Schüßler 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(4):507-510
The NMR satellite frequencies were measured as a function of temperature in the normal high-temperature phase for 87Rb in Rb2ZnBr4 and Rb2ZnCl4 and for 35Cl in betaine calciumchloride dihydrate. Approaching the respective normal-incommensurate phase transition an anomalous shift
of the NMR frequency is observed for the first two cases. This effect is ascribed to the increasing order parameter fluctuations.
The experimental data are compared to calculations which relate the observed behaviour of the NMR frequencies to the non-classical
critical behaviour of the substances under investigation.
Received 6 August 1998 相似文献
3.
N. Keller J. Mistrík Š. Višňovský D.S. Schmool Y. Dumont P. Renaudin M. Guyot R. Krishnan 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(1):67-73
Orthoferrites present, as bulk materials, reorientation transitions of their magnetic moment alignment at temperatures depending
on the rare-earth (RE) ion. In particular, orthoferrites (REFeO3) with RE = Sm, Dy, present this transition at T
SRT = 443 K and 36 K, respectively. The spectra of the complex Kerr and Faraday angle have been measured on orthoferrite thin
films (RE = Sm, Dy, Y), which were prepared by pulsed laser deposition on amorphous quartz substrates. The obtained spectra
exhibit contributions of both surfaces and interfaces. Propagation effects of the polarized light in the magneto-optical medium
which is interpreted in terms of a simplified theoretical formalism, is also observed. For selected photon energies, temperature
dependent Faraday rotation measurements, , on orthoferrite thin films (RE = Sm, Dy, Y) have been performed. A quite different thermal variation compared to the bulk
magnetization has been observed. Curie temperatures are found to be close to the bulk values or slightly larger by 10 K to
20 K as in the case of DyFeO3 and YFeO3. For RE = Sm and Dy, increases with increasing temperature contrary to the saturation magnetization, passes through a maximum at about 460 K and
vanishes with a T
C of 647±18 K, 695 K for RE = Sm and Dy respectively.
Received 28 July 2000 相似文献
4.
P. Fröbrich P.J. Kuntz 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(4):445-455
The many-body Green's function theory developed in our previous work for treating the reorientation of the magnetization of
thin ferromagnetic films is extended to include the exchange anisotropy. This leads to additional momentum dependencies which
require some non-trivial changes in the formalism. The theory is developed for arbitrary spin values S and for multilayers. The effects of the exchange anisotropy and the single-ion anisotropy, which was treated in our earlier
work, on the magnetic properties of thin ferromagnetic films are compared.
Received 31 October 2002 Published online 7 May 2003 相似文献
5.
K. Morawetz C. Olbrich S. Gemming 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):311-317
The coverage of vicinal, stepped surfaces with molecules is simulated with
the help of a two-dimensional Ising model including local distortions and
an Ehrlich-Schwoebel barrier term at the steps. An effective two-spin model is capable
to describe the main properties of this distorted Ising model. It is employed
to analyze the behavior of the system close to the critical points.
Within a well-defined regime of bonding strengths and Ehrlich-Schwoebel barriers we
find a reduction of coverage (magnetization) at low temperatures due to the
presence of the surface step. This results in a second, low-temperature
transition besides the standard Ising order-disorder transition.
The additional transition is characterized by a divergence of the
susceptibility as a finite-size effect. Due to the
surface step the mean-field specific heat diverges with a power law. 相似文献
6.
M.-C. Chung M. Kaulke I. Peschel M. Pleimling W. Selke 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):655-661
The influence of surface defects on the critical properties of magnetic films is studied for Ising models with nearest-neighbour
ferromagnetic couplings. The defects include one or two adjacent lines of additional atoms and a step on the surface. For
the calculations, both density-matrix renormalization group and Monte Carlo techniques are used. By changing the local couplings
at the defects and the film thickness, non-universal features as well as interesting crossover phenomena in the magnetic exponents
are observed.
Received 27 July 2000 and Received in final form 5 October 2000 相似文献
7.
M.E.S. Borelli H. Kleinert A.M.J. Schakel 《The European physical journal. E, Soft matter》2001,4(2):217-221
A stack of tensionless membranes with nonlinear curvature energy and vertical harmonic interaction is studied. At low temperatures,
the system forms a lamellar phase. At a critical temperature, the stack disorders vertically in a melting-like transition.
Received 26 April 2000 and Received in final form 16 August 2000 相似文献
8.
H. Kleinert 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(4):651-658
We point out a possible mechanism by which smooth surfaces can become spiky as the constant of curvature stiffness falls below a certain critical value. This happens either in a single first-order transition, or in a sequence of two Kosterlitz-Thouless-like
transitions. There may also be additional phases in which the spikes form a hexagonal solid-like array or a disordered liquid-like
structure. Our discussion suggests that there exist smooth strings between quarks.
Received 2 September 1998 相似文献
9.
A. Saffarzadeh 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(2):149-153
Spin-polarized tunneling in FMS/M/FMS double tunnel junctions where FMSs are ferromagnetic semiconductor layers and M is a
metal spacer is studied theoretically within the single-site coherent potential approximation (CPA). The exchange interaction
between a conduction electron and localized moment of the magnetic ion is treated in the framework of the s-f model. The spin polarization in the FMS layers is observed to oscillates as a function of the number of atomic planes in
the spacer layer. Amplitude of these oscillations decreases with increasing the exchange interaction in FMS layers.
Received 9 June 2001 and Received in final form 20 August 2001 相似文献
10.
T. Breczewski I. Peral G. Madariaga 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(2):171-176
The ferroelastic domain structure and the phase boundaries of TMCC have been studied in the temperature range 114-90 K by
direct observation under polarised light. By applying an external, compressive and unidirectional mechanical stress the ferroelastic
character of the domain structure has been confirmed. The orientation of the domain walls and phase boundaries are analysed.
To characterise quantitatively the observed domain wall distribution the classical symmetry approach, based on the criterion
of spontaneous strain compatibility, has to be extended to allow small rotations of the domain walls with respect to their
ideal orientation. The observed switching process among the different domains can be understood as a mechanism that minimises
the elastic energy.
Received 21 July 2000 相似文献
11.
E. Popova N. Keller F. Jomard L. Thomas M.-C. Brianso F. Gendron M. Guyot M. Tessier 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):69-74
Magnetic exchange coupling has been observed for ultrathin films of yttrium iron garnet (Y3Fe5O12 or YIG). Single-crystalline YIG films were prepared on yttrium aluminium garnet (Y3Al5O12 or YAG) substrates by pulsed laser deposition. (111) and (110) oriented substrates were used. Film thicknesses were varied
from 180 ? to 4600 ?. Epitaxial growth of YIG on YAG was obtained in spite of the lattice mismatch of 3%. Magnetic hysteresis
loops recorded for ultrathin YIG films have a “bee-waist” shape and show a coupling between two different magnetic phases.
The first phase is magnetically soft YIG. A composition study by secondary ion mass spectroscopy shows the second phase to
be Y3Fe5-xAlxO12 due to the interdiffusion of Fe and Al at the film/substrate interface. This compound is known to be magnetically harder
and to have weaker magnetization than YIG. The coupling of the two phases leads to a hysteresis loop displacement at low temperatures.
This displacement varies differently with film thickness for two substrate orientations. Assuming an interfacial coupling,
the maximal interaction energy is estimated to be about 0.17 erg/cm2 at 5 K for (111) oriented sample.
Received 3 June 2002 / Received in final form 7 October 2002 Published online 27 January 2003
RID="a"
ID="a"Presently at LPM, Université H. Poincaré, BP 239, 54506 Vandœuvre-lès-Nancy e-mail: popova@lpm.u-nancy.fr 相似文献
12.
P. Orgiani C. Aruta G. Balestrino S. Lavanga P.G. Medaglia A. Tebano 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):23-28
Transport properties of SrRuO3 thin films were studied as a function of the epitaxial strain. SrRuO3 films were grown on (100) SrTiO3 substrates by the Pulsed Laser Deposition technique equipped with Reflection High Energy Electrons Diffraction (RHEED). Samples
thickness has been varied from a few unit cells to above 1000 ? while monitoring RHEED intensity oscillations. In thicker
films epitaxial strain was found to be progressively relaxed. SrRuO3 relaxed films (thickness 1000 ?) show metallic behavior for the whole temperature range with a ferromagnetic ordering at about 150 K. For thinner
films, ferromagnetic ordering occurs at progressively lower temperatures, until in films thinner than 400 ? it disappears.
Films thinner than 80 ? show a semiconducting behavior at low temperatures. Our results provide direct evidence of the crucial
role of the strain effect for conducting and magnetic properties of SrRuO3.
Received 16 July 2001 and Received in final form 22 October 2001 相似文献
13.
P. Le Fèvre H. Magnan D. Chandesris 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):555-562
The crystallographic structure of thin Ni films deposited on Cu(001) has been studied using Surface Extended X-ray Absorption
Fine Structure (SEXAFS). Taking advantage of the linear polarization of the synchrotron radiation, we have shown that Ni adopts
the Cu lattice parameter parallel to the interface. This lateral expansion induces a longitudinal compression of the unit
cell, leading to a face centered tetragonal structure of the Ni films from 3 to 10 monolayers. The temperature dependence
of the EXAFS oscillations has allowed to measure strain inside the Ni layers.
Received 22 December 1998 相似文献
14.
I. P. Omelyan W. Fenz R. Folk I. M. Mryglod 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(1):101-110
An integral equation approach is developed to investigate phase
coexistence properties of Ising spin fluids with Yukawa ferromagnetic
and Lennard-Jones nonmagnetic interactions in the presence of an
external field. The calculations are carried out on the basis of
the Duh and Henderson closure with a specific Duh-like partitioning
of the total potential. The coupled set of the Ornstein-Zernike
equation, the closure relation and the external field constraint
are solved using an efficient numerical algorithm. The phase
diagrams are evaluated in a wide range of varying the external
field and the ratio of strengths of Yukawa to Lennard-Jones
interactions. Different types of the phase diagram topology
as well as various external field dependencies of critical
temperatures and densities are identified. The complexity with
respect to simple Lennard-Jones fluids is explained by coupling
between spatial and spin degrees of freedom in the system. A
comparison of the obtained theoretical results with simulation
data is made and a good agreement is observed. 相似文献
15.
In this paper we study tricritical wetting behaviour in three dimensions. In particular we concentrate on systems with short-ranged
forces and apply linear functional renormalization group techniques to elucidate the effect of fluctuations upon tricriticality.
In comparison with studies of critical wetting we identify an additional fluctuation regime which is relevant for values of
the capillary parameter between 2/9 and 1/2. We demonstrate that this regime essentially provides a crossover from mean-field
like behaviour, in which tricritical exponents are always distinct from their critical counterparts, from intermediate- and
strong-fluctuation behaviour where the critical exponents for tricritical and critical wetting are found to always coincide.
We conclude by discussing briefly the possible relevance of these results for experimental studies of wetting.
Received 4 January 2001 and Received in final form 11 May 2001 相似文献
16.
We have studied the effect of physical ageing in thin supported glassy polystyrene films by using ellipsometry to detect overshooting
in the expansivity-temperature curve upon heating of aged samples. Films with thickness 10-200 nm have been aged at 70°
C and 80°
C (below the bulk glass transition temperature). We observe clear relaxation peaks in the expansivity-temperature curve for
films thicker than 18 nm but not for the 10 nm film. The intensity of the relaxation peak is inversely proportional to the
film thickness, while the temperatures characteristic to the relaxation peak are almost independent of the film thickness.
These observations are successfully interpreted by the idea that the surface layer of the order of 10 nm has liquid-like thermal
properties.
Received 28 October 2002 / Published online: 1 April 2003
RID="a"
ID="a"Present address: Yokohama Research Center, Mitsubishi Chemical Corporation, 1000 Kamoshida-chou, Aoba-ku, Yokohama 227-8502, Japan; e-mail:
kawana@rc.m-kagaku.co.jp 相似文献
17.
E.M. de Sousa Luz A.F. Siqueira U.M.S. Costa M.L. Lyra 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(1):115-118
The recent improvements on the technology for developing high-quality thin magnetic films has renewed the interest in the
study of surface effects in both static and dynamic magnetic responses. In this work, we use a Monte-Carlo algorithm with
Metropolis dynamics together with a spreading of damage technique to study the interplay between the effects of finite thickness
and surface ordering field in thin ferromagnetic Ising (S=1/2) films. We calculate, near the bulk critical temperature and several values of the surface field, the dependence on the
film thickness of the average magnetization M and Hamming distance D. We employ a finite size scaling analysis to show that both obey an effective one-parameter scaling but exhibit distinct
characteristic surface fields. At their corresponding characteristic surface fields both M and D become roughly thickness independent and we estimate the critical exponent characterizing the behavior of the typical scaling
lengths.
Received 29 March 1999 and Received in final form 21 April 1999 相似文献
18.
V.V. Savkin A.N. Rubtsov T. Janssen 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(4):525-531
The classical two-dimensional discrete frustrated φ
4
model is studied by Monte Carlo simulations. The correlation function is obtained for two values of a parameter d that determines the frustration in the model. The ground state is a ferro-phase for d
= - 0.35 and a commensurate phase with period N
= 6 for d
= - 0.45. Mean field predicts that at higher temperature the system enters a para-phase via an incommensurate state, in both cases. Monte Carlo data for d
= - 0.45 show two phase transitions with a floating-incommensurate phase between them. The phase transition at higher temperature
is of the Kosterlitz-Thouless type. Analysis of the data for d
= - 0.35 shows only a single phase transition between the floating-fluid phase and the ferro-phase within the numerical error.
Received 16 December 2002 / Received in final form 17 January 2003 Published online 6 March 2003
RID="a"
ID="a"e-mail: vladimir@shg.ru 相似文献
19.
It is shown that orientational ordering of anisotropic organic
molecules with permanent magnetic dipoles in a tilted film should
result in a macroscopic magnetisation in the plane of the film. The
important requirement here is that the molecules are strongly
biaxial, and the corresponding biaxial orientational order parameter
in the tilted phase is sufficiently large. The molecules should also
be characterised by a reduced symmetry of the magnetic core compared
with existing “single molecular magnets". Possible symmetry groups of the
molecular magnetic core, which allow for the existence of nonzero
average magnetic moment, are discussed in detail. The tilt-induced
ferromagnetic ordering of such molecules may be determined by
nonmagnetic intermolecular interactions including, for example,
quadrupole-quadrupole electrostatic interaction or dispersion
interaction between molecules of particular symmetry. Magnetic
intermolecular interactions are not important here, and as a result
the induced ferromagnetic state may be stable in any temperature
range where the corresponding tilted film is stable. These general
conclusions, which form a theoretical foundation for the existence
of novel fluid low-dimensional magnetic materials, are based on
symmetry arguments and are supported by a simple mean-field
molecular model. We also discuss how such induced ferromagnetic
ordering may be observed in Langmuir-Blodgett films which seem to be
the best candidates for preparing these magnetic materials. 相似文献
20.
P. Fröbrich P.J. Jensen P.J. Kuntz A. Ecker 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):579-594
The field-induced reorientation of the magnetization of ferromagnetic films is treated within the framework of many-body Green's
function theory by considering all components of the magnetization. We present a new method for the calculation of expectation
values in terms of the eigenvalues and eigenvectors of the equations of motion matrix for the set of Green's functions. This
formulation allows a straightforward extension of the monolayer case to thin films with many layers and for arbitrary spin
and moreover provides a practicable procedure for numerical computation. The model Hamiltonian includes a Heisenberg term,
an external magnetic field, a second-order uniaxial single-ion anisotropy, and the magnetic dipole-dipole coupling. We utilize
the Tyablikov (RPA) decoupling for the exchange interaction terms and the Anderson-Callen decoupling for the anisotropy terms.
The dipole coupling is treated in the mean-field approximation, a procedure which we demonstrate to be a sufficiently good
approximation for realistic coupling strengths. We apply the new method to monolayers with spin and to multilayer systems with S=1. We compare some of our results to those where mean-field theory (MFT) is applied to all interactions, pointing out some
significant differences.
Received 19 June 2000 and Received in final form 2 August 2000 相似文献