Magnetic and electronic structure of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>(</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ga</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mi>−</mml:mi><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Mn</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mo>)</mml:mo><mml:mi mathvariant="normal">As</mml:mi></mml

Bergqvist, Lars; Korzhavyi, Pavel A.; Sanyal, Biplab; Mirbt, Susanne; Abrikosov, Igor A.; Nordström, Lars; Смирнова, Е. А.; Mohn, P.; Svedlindh, Peter; Eriksson, Olle

doi:10.1103/physrevb.67.205201

Cited by 67 publications

(61 citation statements)

References 54 publications

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“…Critical temperatures have recently been shown to be possible to calculate from first principles theory, by mapping total energy calculations (25,26) to a Heisenberg Hamiltonian or by direct calculation using the local force theorem (27). The statistical part of the problem is then solved by means of Monte Carlo (MC) simulations, and we have followed the work of ref.…”

Section: Resultsmentioning

confidence: 99%

“…The statistical part of the problem is then solved by means of Monte Carlo (MC) simulations, and we have followed the work of ref. 26 to calculate the critical temperature of some of the multilayers shown in Fig. 3.…”

Section: Resultsmentioning

confidence: 99%

“…3. We derived the interatomic exchange interactions by fitting a Heisenberg Hamiltonian to calculated spin-wave energies (26). The Fe 2 V 5 , Fe 3 V 7 , and Fe 4 V 4 multilayers, as well as bulk bcc Fe, were considered in this way.…”

Section: Resultsmentioning

confidence: 99%

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On the sharpness of the interfaces in metallic multilayers

Holmström

Nordström

Bergqvist

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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We show that the three most relevant magnetic properties (magnetic moment, critical temperature, and interlayer exchange coupling) of metallic multilayers can be reproduced with good accuracy by first principles theory, provided that the picture of atomically sharp interfaces is abandoned and one allows instead for both interface alloying and interface roughness. The interface of a metallic multilayer (exemplified by the Fe͞V system) is demonstrated to, at best, have interdiffusion essentially over two to three atomic layers on each side of the interface. Our conclusions are the result of combining experimental work with theoretical modeling, and we argue that this approach is the best avenue to obtain accurate information about the interface quality of metallic multilayers.T he study of physical properties of multilayers (structural, elastic, magnetic, and transport) is one of the most prosperous and rich branches of materials science today (1-3). By growing different atomic layers on top of each other, new phenomena have been observed, e.g., a reduced critical temperature for magnetic ordering, an oscillating interlayer exchange coupling (4), and giant magneto resistance (5). There are several ways in which these properties are used in nanotechnology, using for instance the giant magneto resistance effect (4, 5) in data storage and computer memories. Single-crystal multilayers represent the highest obtainable degree of perfection, with respect to interface and crystalline quality. This type of multilayer is often referred to as a superlattice.Typically, superlattices are grown by molecular beam epitaxy or sputtering. The growth temperature has to be sufficiently high to ensure large surface mobility and thereby enable layer-bylayer growth (6). At the same time, the temperature must be sufficiently low to prevent the metals from interdiffusing and thereby forming alloys. This delicate balance between surface and bulk mobility is of uttermost importance because, as we shall see, all properties that are special for multilayers (interlayer exchange coupling, magnetic moments, and critical temperatures) depend on the interface quality. Although it has been difficult to assess the interface quality in multilayers, it is safe to conclude that an ideal layer-by-layer growth is never obtained.In magnetic superlattices, interface roughness and interface mixing (7) are the most important types of imperfections. These types are schematically illustrated in Fig. 1. In the figure we specify the geometrical extent of the roughness and mixing via the parameters ⌫ T and ⌫ C , respectively. The mixing is assumed to follow a normal distribution with a width specified by ⌫ C . For the roughness we assume that it is composed of terraces with large lateral extent, such that a multilayer of formal composition, e.g., Fe 3 V 7 , may be thought to be composed of multilayers Fe 2 V 8 , Fe 3 V 7 , and Fe 4 V 6 , with a distribution specified by ⌫ T . For details of how the structure of the interface was constructed mathematically, please...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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On the sharpness of the interfaces in metallic multilayers

Holmström

Nordström

Bergqvist

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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“…It is widely expected that new functionalities for electronics and photonics can be derived if the injection, transfer and detection of carrier spin can be controlled above room temperature in these dilute magnetic semiconductors (DMS) 4 . Most of the work in the past has focused on InAs:Mn 5,6,7,8 , GaAs:Mn 9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25 and Ge:Mn 27,28 . Novel control of magnetism has already been achieved in these host materials.…”

Section: Introductionmentioning

confidence: 99%

Jahn-Teller distortion and ferromagnetism in the dilute magnetic semiconductors GaAs:Mn and cubic GaN:Mn

Luo

Martin

2005

Phys. Rev. B

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Using first-principles total-energy methods, we investigate Jahn-Teller distortions in III-V dilute magnetic semiconductors, GaAs:Mn and GaN:Mn in the cubic zinc blende structure. The results for an isolated Mn impurity on a Ga site show that there is no appreciable effect in GaAs, whereas, in GaN there is a Jahn-Teller effect in which the symmetry around the impurity changes from T d to D 2d or to C2v. The large effect in GaN occurs because of the localized d 4 character, which is further enhanced by the distortion. The lower symmetry should be detectable experimentally in cubic GaN with low Mn concentration, and should be affected by charge compensation (reductions of holes and conversion of Mn ions to d 5 with no Jahn-Teller effect). Jahn-Teller effect is greatly reduced because the symmetry at each Mn site is lowered due to the Mn-Mn interaction. The tendency toward ferromagnetism is found to be stronger in GaN:Mn than in GaAs:Mn and to be only slightly reduced by charge compensation.

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“…Our GGA DOS compares well with other theoretical calculations performed within the LDA approach. 16,[25][26][27][28] The first thing to note is that GGA predicts a small gap for both spin-up and spin-down (where the spinup gap appears above the Fermi level, inside unoccupied states; only for spin-down the Fermi level occurs inside the gap demonstrating the half-metallic character). This gap underestimation is usual for GGA.…”

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confidence: 99%

GaMnAs: Position of Mn-d levels and majority spin band gap predicted from GGA-1/2 calculations

Pelá

Marques

Ferreira

et al. 2012

Applied Physics Letters

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Among all magnetic semiconductors, GaMnAs seems to be the most important one. In this work, we present accurate first-principles calculations of GaMnAs within the GGA-1/2 approach: We concentrate our efforts in obtaining the position of the peak of Mn-d levels in the valence band and also the majority spin band gap. For the position of the Mn-d peak, we find a value of 3.3 eV below the Fermi level, in good agreement with the most recent experimental results of 3.5 and 3.7 eV. An analytical expression that fits the calculated Eg(x) for majority spin is derived in order to provide ready access to the band gap for the composition range from 0 to 0.25. We found a value of 3.9 eV for the gap bowing parameter. The results agree well with the most recent experimental data.

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Magnetic and electronic structure of(Ga1−xMnx)As

Cited by 67 publications

References 54 publications

On the sharpness of the interfaces in metallic multilayers

On the sharpness of the interfaces in metallic multilayers

Jahn-Teller distortion and ferromagnetism in the dilute magnetic semiconductors GaAs:Mn and cubic GaN:Mn

GaMnAs: Position of Mn-d levels and majority spin band gap predicted from GGA-1/2 calculations

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