Interfacial and bulk spin Hall contributions to fieldlike spin-orbit torque generated by iridium

We present measurements of spin-orbit torques generated by Ir as a function film thickness in sputtered Ir/CoFeB and Ir/Co samples. find that provides dampinglike component torque with maximum spin-torque conductivity $\phantom{\rule{0.28em}{0ex}}{\ensuremath{\sigma}}_{\mathrm{DL}}^{\mathrm{eff}}=(1.4\phantom{\rule{0.28em}{0ex}}\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0.28em}{0ex}}0.1)\ifmmode\times\else\texttimes\fi{}{10}^{5}\phantom{\rule{0.28em}{0ex}}\frac{\ensuremath{\hbar}}{2e}{\mathrm{\ensuremath{\Omega}}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}$ efficiency ${\ensuremath{\xi}}_{DL}=0.042\ifmmode\pm\else\textpm\fi{}0.005$, which is sufficient to drive switching 0.8 nm CoFeB perpendicular magnetic anisotropy. also observe surprisingly large fieldlike (FLT). Measurements indicate substantial contribution the FLT from an interface mechanism, so ultrathin limit there nonzero $\phantom{\rule{0.28em}{0ex}}{\ensuremath{\sigma}}_{\mathrm{FL}}^{\mathrm{eff}}=\ensuremath{-}(5.0\phantom{\rule{0.28em}{0ex}}\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0.28em}{0ex}}0.5)\ifmmode\times\else\texttimes\fi{}{10}^{4}\phantom{\rule{0.28em}{0ex}}\frac{\ensuremath{\hbar}}{2e}{\mathrm{\ensuremath{\Omega}}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}$. When becomes comparable or greater than its spin diffusion length, $1.6\ifmmode\pm\else\textpm\fi{}0.3\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$, smaller bulk torque.