Spin polarization and Gilbert damping of Co 2Fe(Ga xGe 1-x) Heusler alloys

B. S.D.Ch S. Varaprasad, A. Srinivasan, Y. K. Takahashi, M. Hayashi, A. Rajanikanth, K. Hono*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

75 Citations (Scopus)

Abstract

The spin polarization (P) of ferromagnetic Heusler alloys, Co 2Fe(Ga xGe 1-x) (x = 0, 0.25, 0.5, 0.75, and 1), is investigated by point contact Andreev reflection (PCAR) measurements. While the P values of the ternary Co 2FeGe and Co 2FeGa alloys are 0.58 and 0.59, respectively, the corresponding value for Co 2Fe(Ge 0.5Ga 0.25) is as high as 0.69. Co 2Fe(Ge 0.5Ga 0.5) alloy shows a strong tendency for L2 1 ordering and a high Curie temperature of 807 °C. Ab initio calculations indicate that the band structures of the Co 2FeGe and Co 2Fe(Ge 0.5Ga 0.5) alloys with L2 1 or B2 structures are half-metallic. Thin films of the quaternary Co 2Fe(Ge 0.5Ga 0.5) alloy grown on MgO(0 0 1) substrates order to the L2 1 structure upon annealing at 500 °C, giving rise to a high P of 0.75. This is the highest P value reported for Heusler alloy thin films using the PCAR technique. Ferromagnetic resonance measurements show that the Gilbert damping constant of the film is ∼0.008. All these indicate that the Co 2Fe(Ge 0.5Ga 0.5) alloy is promising as a spin polarized current source for spintronics devices.

Original languageEnglish
Pages (from-to)6257-6265
Number of pages9
JournalActa Materialia
Volume60
Issue number18
DOIs
Publication statusPublished - 2012 Oct
Externally publishedYes

Keywords

  • Ferromagnet
  • Half-metal
  • Heusler alloy
  • Spin polarization

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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