Influence of intermixing at the Ta/CoFeB interface on spin Hall angle in Ta/CoFeB/MgO heterostructures

Monika Cecot*, Łukasz Karwacki, Witold Skowroński, Jarosław Kanak, Jerzy Wrona, Antoni Zywczak, Lide Yao, Sebastiaan van Dijken, Józef Barnaś, Tomasz Stobiecki

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

54 Citations (Scopus)
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Abstract

When a current is passed through a non-magnetic metal with strong spin-orbit coupling, an orthogonal spin current is generated. This spin current can be used to switch the magnetization of an adjacent ferromagnetic layer or drive its magnetization into continuous precession. The interface, which is not necessarily sharp, and the crystallographic structure of the nonmagnetic metal can both affect the strength of current-induced spin-orbit torques. Here, we investigate the effects of interface intermixing and film microstructure on spin-orbit torques in perpendicularly magnetized Ta/Co40Fe40B20/MgO trilayers with different Ta layer thickness (5 nm, 10 nm, 15 nm), greater than the spin diffusion length. Effective spin-orbit torques are determined from harmonic Hall voltage measurements performed at temperatures ranging from 20 K to 300 K. We account for the temperature dependence of damping-like and field-like torques by including an additional contribution from the Ta/CoFeB interface in the spin diffusion model. Using this approach, the temperature variations of the spin Hall angle in the Ta underlayer and at the Ta/CoFeB interface are determined separately. Our results indicate an almost temperature-independent spin Hall angle of {{\boldsymbol{\theta }}}-{{\boldsymbol{SH}}}^{{\boldsymbol{N}}}\approx -{\bf{0}}.{\bf{2}} θ SH N ≈ - 0. 2 in Ta and a strongly temperature-dependent {{\boldsymbol{\theta }}}-{{\boldsymbol{SH}}}^{{\boldsymbol{N}}} θ SH N for the intermixed Ta/CoFeB interface.

Original languageEnglish
Article number968
Pages (from-to)1-11
JournalScientific Reports
Volume7
Issue number1
DOIs
Publication statusPublished - 2017
MoE publication typeA1 Journal article-refereed

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