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First principle study of electronic, magnetic and thermoelectric properties of Co$_2$YPb (Y = Tc, Ti, Zr and Hf) full Heusler: Application to embedded automotive systems

N. Saidi, A. Abbad, W. Benstaali, K. Bahnes

TL;DR

This work uses first-principles density functional theory to investigate structural, electronic, magnetic, elastic and thermoelectric properties of Co$_2$YPb ($Y= ext{Tc, Ti, Zr, Hf}$) full-Heuslers, comparing GGA and mBJ-GGA to improve band-gap predictions. It finds a ferromagnetic Cu$_2$MnAl-type ground state with half-metallic ferromagnetism under mBJ-GGA, integer Slater–Pauling magnetic moments, and robust mechanical stability with ductility. The materials exhibit p-type thermoelectric behavior with large Seebeck coefficients and high, temperature-stable $ZT$ values under an upper-bound assumption, suggesting potential for embedded automotive thermoelectric generators and spintronic applications. The results underscore the viability of Co$_2$YPb alloys for high-temperature spintronics and energy harvesting in automotive contexts, with Tc, Ti, Zr, and Hf variants offering tunable electronic, magnetic and transport properties.

Abstract

In this study, theoretical investigation on structural, electronic, magnetic, elastic and thermoelectric properties of the full Heusler Co$_2$YPb (Y = Tc, Ti, Zr and Hf) alloys have been performed within density functional theory (DFT). The exchange and correlation potential is addressed using two approximations: the generalized gradient approximation (GGA) and the GGA augmented by the Tran--Blaha-modified Becke-Johnson (mBj-GGA) approximation, which provides a more accurate description of the energy band gap. The electronic and magnetic properties reveal that the full-Heusler alloys Co$_2$YPb (with Y = Tc, Ti, Zr, and Hf) display half-metallic ferromagnetic behavior. Furthermore, the elastic properties suggest that Co$_2$YPb are mechanically stable, with ductile characteristics. Full Heusler alloys P-type exhibit positive Seebeck coefficients and high ZT values, indicating good thermoelectric performance in terms of electrical and thermal conductivity. This leads us to the conclusions that these compounds are very interesting in improving the performance of embedded automotive systems and can also be used in spintronic devices.

First principle study of electronic, magnetic and thermoelectric properties of Co$_2$YPb (Y = Tc, Ti, Zr and Hf) full Heusler: Application to embedded automotive systems

TL;DR

This work uses first-principles density functional theory to investigate structural, electronic, magnetic, elastic and thermoelectric properties of CoYPb () full-Heuslers, comparing GGA and mBJ-GGA to improve band-gap predictions. It finds a ferromagnetic CuMnAl-type ground state with half-metallic ferromagnetism under mBJ-GGA, integer Slater–Pauling magnetic moments, and robust mechanical stability with ductility. The materials exhibit p-type thermoelectric behavior with large Seebeck coefficients and high, temperature-stable values under an upper-bound assumption, suggesting potential for embedded automotive thermoelectric generators and spintronic applications. The results underscore the viability of CoYPb alloys for high-temperature spintronics and energy harvesting in automotive contexts, with Tc, Ti, Zr, and Hf variants offering tunable electronic, magnetic and transport properties.

Abstract

In this study, theoretical investigation on structural, electronic, magnetic, elastic and thermoelectric properties of the full Heusler CoYPb (Y = Tc, Ti, Zr and Hf) alloys have been performed within density functional theory (DFT). The exchange and correlation potential is addressed using two approximations: the generalized gradient approximation (GGA) and the GGA augmented by the Tran--Blaha-modified Becke-Johnson (mBj-GGA) approximation, which provides a more accurate description of the energy band gap. The electronic and magnetic properties reveal that the full-Heusler alloys CoYPb (with Y = Tc, Ti, Zr, and Hf) display half-metallic ferromagnetic behavior. Furthermore, the elastic properties suggest that CoYPb are mechanically stable, with ductile characteristics. Full Heusler alloys P-type exhibit positive Seebeck coefficients and high ZT values, indicating good thermoelectric performance in terms of electrical and thermal conductivity. This leads us to the conclusions that these compounds are very interesting in improving the performance of embedded automotive systems and can also be used in spintronic devices.

Paper Structure

This paper contains 15 sections, 2 equations, 10 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Computational details
  3. Results and discussions
  4. Structural properties
  5. Electronic properties
  6. Band structures
  7. Density of states
  8. Magnetic properties
  9. Elastic properties
  10. Thermoelectric properties
  11. Electrical conductivity ($\sigma/\tau$)
  12. Seebeck coefficient ($S$)
  13. Electronic thermal conductivity ($\kappa_e/\tau$)
  14. Figure of merit ($ZT$)
  15. Conclusion

Figures (10)

  • Figure 1: (Colour online) Variation of total energy evolution of the full Heusler Co$_2$YPb alloys (Y = Tc, Ti, Zr and Hf) as a function of unit cell volume, for Cu$_2$MnAl and Hg$_2$CuTi type structures, in FM and NM states.
  • Figure 2: (Colour online) The band structure of the full Co$_2$TcPb Heusler alloys calculated using the GGA and GGA-mBJ approximations to the equilibrium lattice parameter for spin-up and spin-down.
  • Figure 3: (Colour online) The band structure of the full Co$_2$TiPb Heusler alloys calculated using the GGA and GGA-mBJ approximations to the equilibrium lattice parameter for spin-up and spin-down.
  • Figure 4: (Colour online) The band structure of the full Co$_2$ZrPb Heusler alloys calculated using the GGA and GGA-mBJ approximations to the equilibrium lattice parameter for spin-up and spin-down.
  • Figure 5: (Colour online) The band structure of the full Co$_2$HfPb Heusler alloys calculated using the GGA and GGA-mBJ approximations to the equilibrium lattice parameter for spin-up and spin-down.
  • ...and 5 more figures