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Evaluation of spin mixing conductance in ${Co}_{2} Fe {Ga}_{0.5} {Ge}_{0.5} / Pt$ bilayer and the effect of ultrathin Cu, Ni, Ru, Ta, or Cr insertion layers

Madhav M. Bhat ^1,2, H. Suto ^2,*, T. T. Sasaki ², A. Perumal ¹, A. Srinivasan ^1,†, and Y. Sakuraba ^1,2,3

¹Department of Physics, Indian Institute of Technology Guwahati, Guwahati-781039, India
²Research Center for Magnetic and Spintronic Materials, NIMS, Tsukuba 305-0047, Japan
³Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305–8571, Japan

^*Contact author: suto.hirofumi@nims.go.jp
^†Contact author: asrini@iitg.ac.in

Phys. Rev. Materials 10, 054414 – Published 20 May, 2026

DOI: https://doi.org/10.1103/b5xh-ypg7

Abstract

Improving the spin mixing conductance at the ferromagnet/heavy metal (FM/HM) interface with a low Gilbert damping constant in the FM layer is a key requirement for developing efficient spintronic devices. To evaluate the potential of ${Co}_{2} Fe {Ga}_{0.5} {Ge}_{0.5}$ as the FM layers in such structures, epitaxial ${Co}_{2} Fe {Ga}_{0.5} {Ge}_{0.5}$ single-layer and ${Co}_{2} Fe {Ga}_{0.5} {Ge}_{0.5} / Pt$ bilayer films were deposited on MgO substrates using magnetron sputtering, and their Gilbert damping constants were evaluated from ferromagnetic resonance spectra. While the single-layer samples exhibit a low damping constant of $\sim 1.07 \times 10^{- 3}$ , an enhancement in the damping constant was observed in the bilayer samples due to spin pumping across the ${Co}_{2} Fe {Ga}_{0.5} {Ge}_{0.5} / Pt$ interface, from which relatively large spin mixing conductance ( $g_{eff}^{↑ ↓}$ ) of $(2.78 \pm 0.09) \times 10^{19} m^{- 2}$ was evaluated. Further, to investigate the effect of interface property on $g_{eff}^{↑ ↓}$ , ultrathin ( $\sim 0.2$ nm) Cu, Ni, Ru, Ta, or Cr insertion layers were introduced between the ${Co}_{2} Fe {Ga}_{0.5} {Ge}_{0.5}$ and Pt. Inserting a nonmagnetic (NM) Cu layer results in a pronounced decrease of $g_{eff}^{↑ ↓}$ , whereas the FM Ni layer leaves $g_{eff}^{↑ ↓}$ nearly unchanged. In the case of Ru and Ta insertion layers, a modest reduction in $g_{eff}^{↑ ↓}$ is observed despite their NM nature. The antiferromagnetic Cr insertion layer also causes a small decrease in $g_{eff}^{↑ ↓}$ . The observed change in $g_{eff}^{↑ ↓}$ depends on the insertion material, indicating that their physical properties, such as magnetic, nonmagnetic, antiferromagnetic, light or heavy metal, reflect on $g_{eff}^{↑ ↓}$ .

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Madhav. M. Bhat, H. Suto, T. T. Sasaki, A. Perumal, A. Srinivasan, and Y. Sakuraba, Evaluation of spin mixing conductance in ${Co}_{2} {FeGa}_{0.5} {Ge}_{0.5}$ /Pt bilayer and the effect of ultrathin Cu, Ni, Ru, Ta, or Cr insertion layers, https://doi.org/10.48505/nims.6269.

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Evaluation of spin mixing conductance in ${Co}_{2} Fe {Ga}_{0.5} {Ge}_{0.5} / Pt$ bilayer and the effect of ultrathin Cu, Ni, Ru, Ta, or Cr insertion layers

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Evaluation of spin mixing conductance in Co2FeGa0.5Ge0.5/Pt bilayer and the effect of ultrathin Cu, Ni, Ru, Ta, or Cr insertion layers

Abstract

Physics Subject Headings (PhySH)

Article Text

References (36)

Evaluation of spin mixing conductance in ${Co}_{2} Fe {Ga}_{0.5} {Ge}_{0.5} / Pt$ bilayer and the effect of ultrathin Cu, Ni, Ru, Ta, or Cr insertion layers