Stepped Fe(100) and V/Fe(100) Magnetism

1991 ◽  
Vol 231 ◽  
Author(s):  
A. Vega ◽  
A. Rubio ◽  
L.C. Balbas ◽  
J. Dorantes-Davila ◽  
C. Demangeat ◽  
...  
Keyword(s):  
Transition Metal ◽  
Flat Surface ◽  
Magnetic Moments ◽  
Tight Binding ◽  
Step Length ◽  
Real Space ◽  
External Edge ◽  
Transition Metal Surface ◽  
Self Consistent ◽  
Stepped Surface

AbstractWe have investigated the magnetic arrangment of 3d transition-metal stepped surface by using a self-consistent real-space tight-binding method. As expected, the presence of steps modifies locally the properties of a transition-metal surface. We emphasized the influence of atomic environment. We found for the (100)-Fe surface, an enhancement of the magnetic moments of the external edge of this step as compared to the flat surface. The results are not very sensitives to the step length. More striking is the case of the (100)-V stepped surface where atoms at the external edge display a large magnetic moment.

CALCULATION FOR A Cu(001) SURFACE WITH AN IMPURITY ATOM

1999 ◽  
Vol 13 (04) ◽  
pp. 389-396
Author(s):  
CHIH-KAI YANG
Keyword(s):  
Electronic Structure ◽  
Impurity Atom ◽  
Magnetic Moments ◽  
Tight Binding ◽  
Real Space ◽  
Structure Calculation ◽  
Spin Polarized ◽  
Densities Of States ◽  
Self Consistent ◽  
Local Densities

I use a self-consistent electronic structure calculation to study the system of Cu(001) that has an impurity atom replacing one of the surface Cu atoms. The calculation makes use of the tight-binding linear muffin-tin orbitals (TB-LMTO) and is carried out in real space. I am able to derive the spin-polarized local densities of states for the impurity Cr and Fe respectively, which have peaks below the Fermi level. Charge transfers between the impurities and their neighbors also result in different distributions of magnetic moments for the two impurity systems, with the Cr having approximately 0.5μ B and the Fe atom having a negligible magnetic moment.

Structure, Bonding and Stability of Transition Metal Silicides: A Real-Space Perspective by Tight Binding Potentials

1997 ◽  
Vol 491 ◽  
Author(s):  
Leo Miglio ◽  
Francesca Tavazza ◽  
Antonio Garbelli ◽  
Massimo Celino
Keyword(s):  
Molecular Dynamics ◽  
Transition Metal ◽  
Total Energy ◽  
Molecular Dynamics Simulations ◽  
Predictive Power ◽  
Tight Binding ◽  
Real Space ◽  
Energy Calculations ◽  
Metal Silicides ◽  
Dynamics Simulations

ABSTRACTWe point out that the predictive power of tight binding potentials is not limited to obtaining fairly accurate total energy calculations and very satisfactory structural evolutions by molecular dynamics simulations. They also allow for a nice physical picture of the links between bonding and stability in different structures, which is particularly helpful in the case of binary suicides

Transition Metal Impurity-Dislocation Interactions in NiAl: Dislocation Friction and Dislocation Locking

2000 ◽  
Vol 646 ◽  
Author(s):  
O. Yu. Kontsevoi ◽  
Yu.N. Gornostyrev ◽  
A.J. Freeman
Keyword(s):  
Transition Metal ◽  
Central Atom ◽  
Tight Binding ◽  
Electronic States ◽  
Dislocation Core ◽  
Real Space ◽  
Solid Solution Hardening ◽  
Full Potential ◽  
Recursion Method ◽  
Transition Metal Impurity

ABSTRACTThe energetics of the interaction of the <100>{010} edge dislocation in NiAl with early 3d transition metal (TM) impurities was studied using the ab initio real-space tight-binding LMTO-recursion method with 20,000 atom clusters and up to 1,000 non-equivalent atoms in the dislocation core. The coordinates of the atoms in the core were determined within the Peierls-Nabarro (PN) model with restoring forces determined from full-potential LMTO total energy calculations. TM impurities were then placed in different substitutional positions near the dislocation core. For most positions studied, the interaction between impurities and the dislocation is found to be repulsive (dislocation friction). However, when the impurity is in the position close to the central atom of the dislocation core, the interaction becomes strongly attractive, thus causing dislocation locking. Since the size misfit between the Al atom and the substituting TM atom is very small, this locking cannot be explained by elastic (or size misfit) mechanisms; it has an electronic nature and is caused by the formation of the preferred bonding between the electronic states of the impurity atom and the localized electronic states appearing on the central atom of the dislocation core. The calculated results are then discussed in the scope of experimental data on solid solution hardening in NiAl.

Electronic Structure and Transport in Non Periodic Systems: New O(N) Methods

1997 ◽  
Vol 491 ◽  
Author(s):  
D. Mayou ◽  
P. E. A. Turchi ◽  
S. Roche ◽  
J. P. Julien
Keyword(s):  
Linear Response ◽  
Mathematical Theory ◽  
Tight Binding ◽  
Mean Field ◽  
Real Space ◽  
The Self ◽  
Field Theories ◽  
Periodic Systems ◽  
New Approach ◽  
Self Consistent

ABSTRACTThe mathematical theory of orthogonal polynomials and continued fractions provides efficient tools, via the recursion and related methods, for calculating diagonal elements of Green's function of tight-binding Hamiltonians. We present two recent generalizations of this formalism. The first one allows the calculation of conductivity and other linear response coefficients. The second one provides a new approach to the solution of mean-field theories of alloys. In particular it is shown that the self-consistent CPA equations can be easily solved, through a real-space calculation, for multi-component alloys based on periodic or non periodic lattices.

Theoretical Study of the Magnetic Anisotropy of Ni Films on Cu(001)

1997 ◽  
Vol 475 ◽  
Author(s):  
M. Freyss ◽  
R. Lorenz ◽  
H. Dreysse ◽  
J. Hafner
Keyword(s):  
Magnetic Anisotropy ◽  
Theoretical Study ◽  
Magnetic Moments ◽  
Tight Binding ◽  
Real Space ◽  
Spin Orbit Coupling ◽  
Magnetization Direction ◽  
Out Of Plane ◽  
Lmto Method ◽  
The Stability

ABSTRACTThe anisotropy properties of Ni films on Cu(001) are quite unusual compared to other systems: The magnetization direction of Ni is in-plane for a coverage smaller than a critical thickness of 7 monolayers and out-of-plane for a coverage larger than 7 monolayers. As a first step in the study of this unusual behaviour, we report results of ab-initio calculations of the magnetic order of Ni films on a Cu(001) substrate. The magnetic moments are computed by means of the real-space Tight-Binding LMTO method allowing non-collinear magnetic moments and including spin-orbit coupling to account for magnetic anisotropy effects. As the number of Ni layers is increased, we discuss the stability of the system with a magnetization in-plane or out-of-plane.

EXCHANGE COUPLING IN Fe/Pd/Fe TRILAYERS

1993 ◽  
Vol 07 (01n03) ◽  
pp. 452-455
Author(s):  
H. NAIT-LAZIZ ◽  
S. BOUARAB ◽  
C. DEMANGEAT ◽  
A. MOKRANI ◽  
H. DREYSSE
Keyword(s):  
Surface Roughness ◽  
Exchange Coupling ◽  
Magnetic Moments ◽  
Real Space ◽  
Hubbard Hamiltonian ◽  
Interface Surface ◽  
Number Of Layers ◽  
Self Consistent ◽  
Space Description

The exchange coupling in Fe/Pd/Fe trilayers is investigated through self-consistent real-space description of the Hubbard Hamiltonian. For both ferromagnetic (F) and antiferromagnetic (AF) couplings between Fe layers, the Pd layers are shown to be polarized. However, the AF coupling between Fe layers reduces strongly the Pd polarization displayed in the case of F coupling. Also, the magnetic moments of the Fe atoms at the Fe/Pd interface are smaller in the AF coupling as compared to the F one. Up to five layers of Pd, the F coupling is found stable. For 6 layers of Pd, the AF coupling becomes more stable. This result compares qualitatively with the experiment of Celinski and Heinrich, but the number of layers neccessary to move from F to AF is smaller than that reported experimentally. The quantitative disagreement may be related to the relaxation at the interface, surface roughness or/and interdiffusion which are not considered in this study.

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