Rádio ZET, 21.11.2017.
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Physical properties of the CuMnAs alloy - promising material for the antiferromagnetic spintronics
CuMnAs is now an extensively studied promising material for the antiferromagnetic spintronics. CuMnX Heusler alloys cannot be grown without defects. It is difficult to estimate precise sample stoichiometry by X-ray analysis due to very similar scattering properties of Cu and Mn atoms and also a reliable neutron diffraction analysis for real samples is not available. Computer simulations are an effective tool to find most probable defects and relate their concentrations to measured transport characteristics.
We have investigated from first principles the role of defects in the antiferromagnetic CuMnAs alloy with tetragonal structure [1] as well as for the prototype Heusler alloy CuMnSb [2]. MnCu, CuMn, Mn↔Cu swaps, and vacancies on Mn- and Cu-sublattices are the most probable defects in these materials. We have found that for both systems the electron correlations play important role in description of the phase stability and that the antiferromagnetic [111]-ground state of CuMnSb is stabilized by impurity concentrations of approximately 3%. On the other hand for the tetragonal CuMnAs the effect of defects is weak.
We calculated transport properties for CuMnAs with defects of low formation energies and estimated in-plane resistivity of CuMnAs. Our numerical simulations fitted experiment very well if we assumed concentrations 3.5-5% MnCu or Mn↔Cu swaps, much larger concentrations would be needed for CuMn defects or Mn-vacancies. We have estimated also the N´eel temperature using the Monte Carlo approach for CuMnAs, result agrees reasonably well with the experimentally observed value.
[1]
F. Máca, J. Kudrnovský, V. Drchal, K. Carva, P. Baláž, and I. Turek, Phys. Rev. B 96 (2017) 094406.
[2] F. Máca, J. Kudrnovský, V. Drchal, I. Turek, O. Stelmakhovych, P. Beran, A. Llobet and X. Marti, Phys. Rev. B 94(2016) 094407.
We have investigated from first principles the role of defects in the antiferromagnetic CuMnAs alloy with tetragonal structure [1] as well as for the prototype Heusler alloy CuMnSb [2]. MnCu, CuMn, Mn↔Cu swaps, and vacancies on Mn- and Cu-sublattices are the most probable defects in these materials. We have found that for both systems the electron correlations play important role in description of the phase stability and that the antiferromagnetic [111]-ground state of CuMnSb is stabilized by impurity concentrations of approximately 3%. On the other hand for the tetragonal CuMnAs the effect of defects is weak.
We calculated transport properties for CuMnAs with defects of low formation energies and estimated in-plane resistivity of CuMnAs. Our numerical simulations fitted experiment very well if we assumed concentrations 3.5-5% MnCu or Mn↔Cu swaps, much larger concentrations would be needed for CuMn defects or Mn-vacancies. We have estimated also the N´eel temperature using the Monte Carlo approach for CuMnAs, result agrees reasonably well with the experimentally observed value.
The elementary cell of tetragonal CuMnAs. Arrows mark the orientation of magnetic moments in the antiferromagnetic alloy. |
[2] F. Máca, J. Kudrnovský, V. Drchal, I. Turek, O. Stelmakhovych, P. Beran, A. Llobet and X. Marti, Phys. Rev. B 94(2016) 094407.
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