Role of structural defects on the half-metallic character of Co 2MnGe and Co2MnSi Heusler alloys

S. Picozzi, A. Continenza, Arthur J Freeman

Research output: Contribution to journalArticle

322 Citations (Scopus)

Abstract

Heusler alloys, such as Co2MnSi and Co2MnGe, have been predicted from first-principles to be half metallic and potential candidates for spintronic applications. However, spin polarizations of only 50-60 % were experimentally obtained for these compounds - a decrease attributed to defects in the Mn and Co sublattices. Accurate ab initio full-potential linearized augmented plane wave calculations are performed in order to determine the effects of several types of defects (such as antisites and atomic swaps) on the electronic and magnetic properties of the bulk Heusler compounds. Our findings, in general agreement with experiments, show that Mn antisites have the lowest formation energy and retain the half-metallic character. On the other hand, Co antisites have a slightly higher formation energy and a dramatic effect on the electronic properties: the defect states that locally destroy half metallicity are energetically localized and are screened out in a couple of atomic shells. In this case, the spin polarization at the Fermi level is strongly reduced, and the spin polarization due to the s electrons, responsible for the tunneling current, is in excellent agreement with experiment. Finally, both Mn-Si and Mn-Co atomic swaps have very high formation energies, keeping however the half-metallic character.

Original languageEnglish
Article number094423
Pages (from-to)944231-944237
Number of pages7
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume69
Issue number9
Publication statusPublished - Mar 2004

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Spin polarization
energy of formation
Electronic properties
Defects
defects
polarization
Magnetoelectronics
Fermi level
electronics
sublattices
metallicity
Magnetic properties
plane waves
Experiments
magnetic properties
Electrons
electrons

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Role of structural defects on the half-metallic character of Co 2MnGe and Co2MnSi Heusler alloys. / Picozzi, S.; Continenza, A.; Freeman, Arthur J.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 69, No. 9, 094423, 03.2004, p. 944231-944237.

Research output: Contribution to journalArticle

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N2 - Heusler alloys, such as Co2MnSi and Co2MnGe, have been predicted from first-principles to be half metallic and potential candidates for spintronic applications. However, spin polarizations of only 50-60 % were experimentally obtained for these compounds - a decrease attributed to defects in the Mn and Co sublattices. Accurate ab initio full-potential linearized augmented plane wave calculations are performed in order to determine the effects of several types of defects (such as antisites and atomic swaps) on the electronic and magnetic properties of the bulk Heusler compounds. Our findings, in general agreement with experiments, show that Mn antisites have the lowest formation energy and retain the half-metallic character. On the other hand, Co antisites have a slightly higher formation energy and a dramatic effect on the electronic properties: the defect states that locally destroy half metallicity are energetically localized and are screened out in a couple of atomic shells. In this case, the spin polarization at the Fermi level is strongly reduced, and the spin polarization due to the s electrons, responsible for the tunneling current, is in excellent agreement with experiment. Finally, both Mn-Si and Mn-Co atomic swaps have very high formation energies, keeping however the half-metallic character.

AB - Heusler alloys, such as Co2MnSi and Co2MnGe, have been predicted from first-principles to be half metallic and potential candidates for spintronic applications. However, spin polarizations of only 50-60 % were experimentally obtained for these compounds - a decrease attributed to defects in the Mn and Co sublattices. Accurate ab initio full-potential linearized augmented plane wave calculations are performed in order to determine the effects of several types of defects (such as antisites and atomic swaps) on the electronic and magnetic properties of the bulk Heusler compounds. Our findings, in general agreement with experiments, show that Mn antisites have the lowest formation energy and retain the half-metallic character. On the other hand, Co antisites have a slightly higher formation energy and a dramatic effect on the electronic properties: the defect states that locally destroy half metallicity are energetically localized and are screened out in a couple of atomic shells. In this case, the spin polarization at the Fermi level is strongly reduced, and the spin polarization due to the s electrons, responsible for the tunneling current, is in excellent agreement with experiment. Finally, both Mn-Si and Mn-Co atomic swaps have very high formation energies, keeping however the half-metallic character.

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