Interaction of Magnetic Impurities with Surfaces

1997 ◽  
Vol 475 ◽  
Author(s):  
L. Szunyogh ◽  
B.L. Györffy
Keyword(s):  
Thin Films ◽  
Fermi Surface ◽  
Magnetic Anisotropy ◽  
First Principles ◽  
Anisotropy Constant ◽  
Thickness Dependence ◽  
Magnetic Impurities ◽  
First Principles Calculations ◽  
Spin Polarized ◽  
Fe Impurity

ABSTRACTThe interaction of a magnetic (Fe) impurity with the surface of a non-magnetic (Au) semi-infinite host is investigated in terms of fully relativistic spin-polarized first principles calculations. It is shown that the surface induces a magnetic anisotropy on the impurity which is considerably larger than in the bulk. It is also found that the anisotropy constant K(d) is an oscillating function of the distance d between the impurity and the surface with an amplitude which falls as 1/d2 and a period which is determined by the shape of the Fermi Surface of the bulk Au host. However, the question still remains open whether the magnitude of the anisotropy energy is sufficiently large to explain the thickness dependence of the Kondo amplitude B in thin films of dilute FecAu1-c alloys.

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

Exchange Bias in CrO2/Cr2O3 Bilayer Thin Films

2006 ◽  
Vol 45 ◽  
pp. 2528-2533 ◽  
Author(s):  
S. Srinath ◽  
N.A. Frey ◽  
H. Srikanth ◽  
G.X. Miao ◽  
A. Gupta
Keyword(s):  
Thin Films ◽  
Magnetic Anisotropy ◽  
Variable Thickness ◽  
Exchange Bias ◽  
Exchange Coupling ◽  
Hysteresis Loops ◽  
Anisotropy Constant ◽  
Effective Magnetic Anisotropy ◽  
Large Anisotropy

We have investigated the exchange bias in CVD grown epitaxial CrO2/Cr2O3 bilayer thin films using hysteresis loops and resonant RF transverse susceptibility. M-H loops indicated an enhanced coercivity without appreciable loop shift and the transverse susceptibility in CrO2/Cr2O3 bilayers revealed features associated with both the ferromagnetic and antiferromagnetic phases. In addition, TS yielded large anisotropy constant (Keff) values depending on the fraction of Cr2O3 present. The large anisotropy fields observed cannot be accounted for by the variable thickness of CrO2 alone and are indicative of possible exchange coupling between CrO2 and Cr2O3 phases that significantly affects the effective magnetic anisotropy.

FIRST PRINCIPLES DENSITY FUNCTIONAL INVESTIGATION OF SUPPORTED TUNGSTEN CLUSTER (Wn; n = 1 TO 6) ON ANCHORED GRAPHITE (0001) SURFACE

2013 ◽  
Vol 02 (03n04) ◽  
pp. 1350015
Author(s):  
SONALI BARMAN ◽  
G. P. DAS ◽  
Y. KAWAZOE
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Metal Clusters ◽  
Theoretical Study ◽  
First Principles Calculations ◽  
Novel Technique ◽  
Defect Site ◽  
Positive Ions ◽  
Spin Polarized ◽  
Functional Investigation

Size-selected Wn clusters can be deposited firmly on a graphite (0001) surface using a novel technique, where the positive ions (of the same metal atom species) embedded on the graphite surface by ion implantation, act as anchors. The size selected metal clusters can then soft land on this anchored surface m [Hayakawa et al., 2009]. We have carried out a systematic theoretical study of the adsorption of Wn (n = 1-6) clusters on anchored graphite (0001) surface, using state-of-art spin-polarized density functional approach. In our first-principles calculations, the graphite (0001) surface has been suitably modeled as a slab separated by large vacuum layers. Wn clusters bond on clean graphite (0001) surface with a rather weak Van-der-Waals interaction. However, on the anchored graphite (0001) surface, the Wn clusters get absorbed at the defect site with a much larger adsorption energy. We report here the results of our first-principles investigation of this supported Wn cluster system, along with their reactivity trend as a function of the cluster size (n).

Initial stages of the adsorption of Sc and ScN thin films on GaN(0001): First principles calculations

2013 ◽  
Vol 268 ◽  
pp. 16-21 ◽  
Author(s):  
J. Guerrero-Sánchez ◽  
Gregorio H. Cocoletzi ◽  
J.F. Rivas-Silva ◽  
Noboru Takeuchi
Keyword(s):  
Thin Films ◽  
First Principles ◽  
First Principles Calculations
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