Spin-orbit-proximitized ferromagnetic metals in spintronic phenomena: A first-principles Green’s function approach

The talk reviews first-principles Green’s function methodology to obtain spectral function and spin texture at an arbitrary plane around interfaces within multilayers of different materials [1]. When applied to ultrathin ferromagnetic layer in contact with a material with strong spin-orbit coupling-such as topological insulators, heavy metals, monolayer transition metal dichalcogenides and Weyl semimetals (all of which have been utilized very recently to develop novel spintronic devices and they will be discussed in the talk)-this methodology reveals dramatic modification of ferromagnet electron and spin structures which acquire properties of the adjacent layer due to hybridization of their wave functions. In particular, such spin-orbit-proximitized ferromagnetic layer acquires spin textures that are noncollinear to its own magnetization. Passing unpolarized charge current parallel to the interface generates nonequilibrium spin density [2] in the presence of such textures, which becomes resource for spintronic devices operated by spin-orbit torques [3]. On the other hand, passing spin-polarized charge current or pure spin current perpendicular to the interface leads to spin memory loss due to the same spin textures [4] (even in the absence of disorder, intermixing and magnons at the interface) which adversely affects spintronic device operation. The talk will explain how to model spin-orbit torques and spin memory loss by employing first-principles Green’s functions to construct relevant nonequilibrium density matrices [3,4].

References:

[1] J. M. Marmolejo-Tejada, K. Dolui, P. Lazić, P.-H. Chang, S. Smidstrup, D. Stradi, K. Stokbro, and B. K. Nikolić, Nano Lett. 17, 5626 (2017).
[2] P.-H. Chang, T. Markussen, S. Smidstrup, K. Stokbro, and B. K. Nikolić, Phys. Rev. B 92, 201406(R) (2015).
[3] B. K. Nikolić, K. Dolui, M. Petrović, P. Plecháč, T. Markussen, and K. Stokbro, https://arxiv.org/abs/1801.05793.
[4] K. Dolui and B. K. Nikolić, Phys. Rev. B 96, 220403 (2017).