Structural Phase-Dependent Giant Interfacial Spin Transparency in W/CoFeB Thin-Film Heterostructures

Surya Narayan Panda; Sudip Majumder; Arpan Bhattacharyya; Soma Dutta; Samiran Choudhury; Anjan Barman

doi:10.1021/acsami.1c03776

Structural Phase-Dependent Giant Interfacial Spin Transparency in W/CoFeB Thin-Film Heterostructures

ACS Appl Mater Interfaces. 2021 May 5;13(17):20875-20884. doi: 10.1021/acsami.1c03776. Epub 2021 Apr 22.

Authors

Surya Narayan Panda¹, Sudip Majumder¹, Arpan Bhattacharyya¹, Soma Dutta¹, Samiran Choudhury¹, Anjan Barman¹

Affiliation

¹ Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India.

PMID: 33886256
DOI: 10.1021/acsami.1c03776

Abstract

Pure spin current has transformed the research field of conventional spintronics due to its various advantages, including energy efficiency. An efficient mechanism for generation of pure spin current is spin pumping, and high effective spin-mixing conductance (G_eff) and interfacial spin transparency (T) are essential for its higher efficiency. By employing the time-resolved magneto-optical Kerr effect technique, we report here a giant value of T in substrate/W (t)/Co₂₀Fe₆₀B₂₀ (d)/SiO₂ (2 nm) thin-film heterostructures in the beta-tungsten (β-W) phase. We extract the spin diffusion length of W and spin-mixing conductance of the W/CoFeB interface from the variation of damping as a function of W and CoFeB thickness. This leads to a value of T = 0.81 ± 0.03 for the β-W/CoFeB interface. A stark variation of G_eff and T with the thickness of the W layer is obtained in accordance with the structural phase transition and resistivity variation of W with its thickness. Effects such as spin memory loss and two-magnon scattering are found to have minor contributions to damping modulation in comparison to the spin pumping effect which is reconfirmed from the unchanged damping constant with the variation of Cu spacer layer thickness inserted between W and CoFeB. The giant interfacial spin transparency and its strong dependence on crystal structures of W will be important for future spin-orbitronic devices based on pure spin current.

Keywords: Gilbert damping parameter; interfacial spin transparency; spin pumping; spin-mixing conductance; thin-film heterostructures; time-resolved magneto-optical Kerr effect.