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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.
P. Politi M.G. Pini 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(4):475-481
We study the effect of dipolar interactions on a magnetic striped monolayer with a microscopic unit cell of square symmetry,
and of size spins. Even if the aspect ratio r=N
x
/N
y
is very large, an in-plane shape anisotropy is always negligible, except if Ny is fairly small (N
y
<40). In-plane domains are not possible, except for values of the dipolar coupling larger than the domain wall energy.
Received: 11 July 1997 / Revised: 24 September 1997 / Accepted: 24 October 1997 相似文献
3.
R. Tigrine A. Khater B. Bourahla M. Abou Ghantous O. Rafil 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(1):59-64
A theoretical model is presented for the study of the scattering of magnons
at an extended symmetric atomic well in very thin magnetic films. The thin
film consists of three cubic atomic planes with ordered spins coupled by
Heisenberg exchange, and the system is supported on a non-magnetic
substrate, and considered otherwise free from magnetic interactions. The
coherent transmission and reflection scattering coefficients are derived as
elements of a Landauer type scattering matrix. Transmission and reflection
scattering cross sections are hence calculated specifically, as a function
of the varying local magnetic exchange on the inhomogeneous boundary.
Detailed numerical results for the individual incident film magnons, and for
the calculated overall magnon conductance, show characteristic transmission
properties, with associated Fano resonances, depending on the magnetic
boundary conditions and on the magnon incidence. 相似文献
4.
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
5.
P. Fröbrich P.J. Jensen P.J. Kuntz 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(3):477-489
The reorientation of the magnetization of a ferromagnetic monolayer is calculated with the help of many-body Green's function
theory. This allows, in contrast to other spin wave theories, a satisfactory calculation of magnetic properties over the entire
temperature range of interest since interactions between spin waves are taken into account. A Heisenberg Hamiltonian plus
a second-order uniaxial single-ion anisotropy and an external magnetic field is treated by the Tyablikov (Random Phase Approximation:
RPA) decoupling of the exchange interaction term and the Anderson-Callen decoupling of the anisotropy term. The orientation
of the magnetization is determined by the spin components (), which are calculated with the help of the spectral theorem. The knowledge of the orientation angle allows a non-perturbative determination of the temperature dependence of the effective second-order anisotropy coefficient.
Results for the Green's function theory are compared with those obtained with mean-field theory (MFT). We find significant
differences between these approaches.
Received 6 April 1999 and Received in final form 9 July 1999 相似文献
6.
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
7.
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
8.
F. Körmann S. Schwieger J. Kienert W. Nolting 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(4):463-469
We present a new type of temperature driven spin reorientation transition (SRT) in thin films. It can occur when the lattice
and the shape anisotropy
favor different easy directions of the magnetization. Due to different temperature dependencies of the two contributions the
effective anisotropy
may change its sign and thus the direction of the magnetization as a function of temperature may change. Contrary to the well-known
reorientation transition caused by
competing surface and bulk anisotropy contributions the reorientation that we discuss is also found in film systems with a
uniform lattice anisotropy.
The results of our theoretical model study may have experimental relevance for film systems with positive lattice anisotropy,
as e.g. thin iron films grown on copper. 相似文献
9.
P. Schieffer C. Krembel M.-C. Hanf M.-H. Tuilier P. Wetzel G. Gewinner K. Hricovini 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(2):165-168
We studied the magnetic properties of ultra-thin Mn films deposited on Ag (001) held at 80 K with soft X-ray absorption and
magnetic circular dichroism. The observed shape and branching ratio of the Mn 2p absorption edge as a function of Mn coverage demonstrate that, up to , the Mn adopts a stable high spin state similar to the Mn atom Hund's rule 6
S
5/2
ground state. Above this coverage a rapid transition from localized high spin to itinerant low spin behavior of the Mn 3d electrons is evidenced. Magnetic circular dichroism shows no sign of long range ferromagnetic order in these films at 80
K. The data, first confirm the large atomic-like local magnetic moment, and second are in line with the in-plane antiferromagnetic order, reported recently (Phys. Rev. B 57, 1141 (1998)), for Mn in the nearly ideal on-top Mn monolayer formed by 0.9 ML deposited at 80 K.
Received: 4 May 1998 相似文献
10.
S. Bhattacharjee S. M. Jaya 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(3):305-311
The influence of correlation and temperature on the electronic structure of bulk and
thin film GdN
has been studied using the s-f model, which combines
the one electron band structure with a many body procedure.
The tight binding linear muffin tin orbital (TB-LMTO) method was used to obtain
the one electron band structure of
the system. The s-f exchange coupling constants
for each band were obtained from the spin polarized band structure of
the system using a mean field model.
Correlation effects are found to be present in the system. However they
are not sufficiently strong to cause a correlation induced splitting in the
spectrum. Some bands of the thin films of GdN exhibit splitting at T=Tc
and it is due to the combined effect
of correlation and temperature. The conduction bands of both the bulk and
the thin films of GdN exhibit a red shift with respect to temperature. 相似文献
11.
N. Rehse C. Wang M. Hund M. Geoghegan R. Magerle G. Krausch 《The European physical journal. E, Soft matter》2001,4(1):69-76
We study the wetting behaviour of thin polystyrene (PS) films on regularly corrugated silicon substrates. Below a critical
film thickness the PS films are unstable and dewet the substrates. The dewetting process leads to the formation of nanoscopic
PS channels filling the grooves of the corrugated substrates. Films thicker than the critical thickness appear stable and
follow the underlying corrugation pattern. The critical thickness is found to scale with the radius of gyration of the unperturbed
polymer chains.
Received 6 April 2000 and Received in final form 24 August 2000 相似文献
12.
S. Soriano C. Dufour K. Dumesnil Ph. Mangin 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):469-478
Below its ordering temperature (T
N
= 90 K), bulk bcc Eu has a helical magnetic state with propagation vectors along the three equivalent 〈100〉 directions. In
contrast, epitaxial (110)Eu films exhibit a unique magnetic ordering: the domain with a magnetic helix propagating along the
in-plane [001] direction vanishes on cooling, at the expense of other domains with helices propagating along [100] and [010].
This paper is devoted to the study of the stability of the magnetic domains in an external magnetic field using neutron scattering
experiments and macroscopic magnetization measurements. The helix propagating along the [001] direction can be restored by
the application of an external field along this direction. On the contrary, when a magnetic field is applied along an intermediate
direction, specifically [10], the domain with a helix propagating along [001] is suppressed. Both effects depend on the film thickness. They are explained
if one considers that, because of the low magnetic anisotropy of Eu, a helix with a propagation vector parallel to (or close
to) the applied magnetic field is energetically more favourable than cycloidal structures with unchanged propagation vectors.
Finally, the amplitudes of the propagation vectors and their directions (that are modified in films compared to bulk) do not
vary under magnetic field. 相似文献
13.
We study large scale surface deformations of a liquid film
unstable due to the Marangoni effect caused by external heating
on a smooth and solid substrate. The work is based on the thin
film equation which can be derived from the basic hydrodynamic
equations. To prevent rupture, a repelling disjoining pressure
is included which accounts for the stabilization of a thin
precursor film and so prevents the occurrence of completely dry
regions. Linear stability analysis, nonlinear stationary
solutions, as well as three-dimensional time dependent numerical
solutions for horizontal and inclined substrates reveal a rich
scenario of possible structures for several realistic fluid
parameters. 相似文献
14.
Rauscher M Münch A Wagner B Blossey R 《The European physical journal. E, Soft matter》2005,17(3):373-379
We derive a novel thin-film equation for linear viscoelastic media describable by generalized Maxwell or Jeffreys models. As a first application of this equation we discuss the shape of a liquid rim near a dewetting front. Although the dynamics of the liquid is equivalent to that of a phenomenological model recently proposed by Herminghaus et al. (S. Herminghaus, R. Seemann, K. Jacobs, Phys. Rev. Lett. 89, 056101 (2002)), the liquid rim profile in our model always shows oscillatory behaviour, contrary to that obtained in the former. This difference in behaviour is attributed to a different treatment of slip in both models. 相似文献
15.
Carvalho AJ Pereira-da-Silva MA Faria RM 《The European physical journal. E, Soft matter》2006,20(3):309-315
Self-organized block copolymer structures derived from dewetting of thin films are becoming important in nanotechnology because
of the various spontaneous and regular sub-micrometric surface patterns that may be obtained. Here, we report on the self-organization
of a poly(styrene)-b-poly(ethene-co-butene-1)-b-poly(styrene) triblock copolymer during drying of its solution over a mica
substrate. Regular submicrometric arrangements with long-range order were formed at critical polymer concentrations, consisting
of parallel ribbons and hexagonal arrays of dots (droplets). This variety of highly ordered structures is explained by the
interplay between forming mechanisms, mainly due to “fingering instabilities” at the three-phase line of the copolymer solution
during drying. The thickness of the structures was “quantized” due to the microphase separation of the block copolymer. The
formation of hexagonal patterns may be attributed to Marangoni instability at the liquid film surface prior to dewetting. 相似文献
16.
Blossey R Münch A Rauscher M Wagner B 《The European physical journal. E, Soft matter》2006,20(3):267-271
Ultrathin polymer films on non-wettable substrates display dynamic features which have been attributed to either viscoelastic
or slip effects. Here we show that in the weak- and strong-slip regime, effects of viscoelastic relaxation are either absent
or essentially indistinguishable from slip effects. Strong slip modifies the fastest unstable mode in a rupturing thin film,
which questions the standard approach to reconstruct the effective interface potential from dewetting experiments. 相似文献
17.
V. Faucheux 《Applied Surface Science》2006,252(15):5504-5507
18.
We study the dewetting of thin polymer films deposited on slippery substrate. Recent experiments on these systems have revealed
many unexpected features. We develop here a model that takes into account the rheological properties of polymer melts, focussing
on two dewetting geometries (the receding of a straight edge, and the opening of a hole). We show that the friction law associated
with the slippage between the film and the substrate has a direct influence on the dewetting dynamic. In addition, we demonstrate
that residual stresses, which can be stored in the films due to their viscoelasticity, are a source of destabilization for
polymer films, and accelerate the dewetting process. 相似文献
19.
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
20.
Münch A Wagner B Rauscher M Blossey R 《The European physical journal. E, Soft matter》2006,20(4):365-368
We derive a thin-film model for viscoelastic liquids under strong slip which obey the stress tensor dynamics of corotational
Jeffreys fluids. 相似文献