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- Lebegue, Sebastien, et al.
(författare)
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Electronic structure and spectroscopic properties of thulium monochalcogenides
- 2005
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Ingår i: PHYSICAL REVIEW B. - 1098-0121. ; 72:24, s. 245102-
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of the thulium monochalcogenides TmS, TmSe, and TmTe is studied with several theoretical approaches. The total energy is evaluated with the self-interaction corrected local-spin density approximation, whereby the Tm ions are described with either twelve or thirteen localized f electrons with the remaining electrons forming bands. The comparisons of these two scenarios reveal the valency shift of the Tm ion through the series. The spectral functions of TmX compounds are calculated including multiplet effects, and they are compared to experimental x-ray photoemission spectra. The basic tool is the Hubbard-I approximation in which the embedding of an isolated f(n) ion in a solid is performed by modifying the crystal Hamiltonian as obtained from the local-density approximation with the atomic self-energy of the ion. The parameters of the model are obtained from the self-consistent band structure calculation. The agreement with experiment is excellent, reproducing all significant multiplet structures.
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- Sanyal, Biplab, et al.
(författare)
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Electronic structure and magnetism of Mn-doped GaN
- 2003
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 68:20, s. 205210-
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Tidskriftsartikel (refereegranskat)abstract
- Mn-doped semiconductors are extremely interesting systems due to their novel magnetic properties suitable for the spintronics applications. It has been shown recently by both theory and experiment that Mn-doped GaN systems have a very high Curie temperature compared to that of Mn-doped GaAs systems. To understand the electronic and magnetic properties, we have studied Mn-doped GaN system in detail by a first-principles plane-wave method. We show here the effect of varying Mn concentration on the electronic and magnetic properties. In agreement with previous studies, d states of Mn form an impurity band completely separated from the valence-band states of the host GaN for dilute Mn concentration. This is in contrast to the Mn-doped GaAs system where Mn d states in the gap lie very close to the valence-band edge and hybridize strongly with the delocalized valence-band states. To study the effects of electron correlation, LSDA+U calculations have been performed. Calculated exchange interaction in (Mn,Ga)N is short ranged contrary to that in (Mn,Ga)As where the strength of the ferromagnetic coupling between Mn spins is not decreased substantially for large Mn-Mn separation. Also, the exchange interactions are anisotropic in different crystallographic directions due to the presence or absence of connectivity between Mn atoms through As bonds.
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- Skubic, Björn, et al.
(författare)
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Competing Exchange Interactions in Magnetic Multilayers
- 2006
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 96, s. 057205-
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Tidskriftsartikel (refereegranskat)abstract
- We have studied alloying of the nonmagnetic spacer layer with a magnetic material as a method of tuning the interlayer coupling in magnetic multilayers. We have specifically studied the Fe/V(100) system by alloying the spacer V with various amounts of Fe. For some Fe concentrations in the spacer, it is possible to create a competition between antiferromagnetic Ruderman-Kittel-Kasuya-Yoshida exchange and direct ferromagnetic exchange coupling. The exchange coupling and transport properties for a large span of systems with different spacer concentrations and thicknesses were calculated and measured experimentally and good agreement between observations and theory was observed. A reduction in magnetoresistance of about 50% was observed close to the switchover from antiferromagnetic to ferromagnetic coupling.
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