Determination of spin Hall angle, spin mixing conductance, and spin diffusion length in CoFeB/Ir for spin-orbitronic devices

Abstract

Iridium is a very promising material for spintronic applications due to its interesting magnetic properties such as large RKKY exchange coupling as well as its large spin-orbit coupling value. Ir is for instance used as a spacer layer for perpendicular synthetic antiferromagnetic or ferrimagnet systems. However, only a few studies of the spintronic parameters of this material have been reported. In this paper, we present inverse spin Hall effect -spin pumping ferromagnetic resonance measurements on CoFeB/Ir based bilayers to estimate the values of the effective spin Hall angle, the spin diffusion length within iridium, and the spin mixing conductance in the CoFeB/Ir bilayer. In order to have reliable results, we performed the same experiments on CoFeB/Pt bilayers, which behavior is well known due to numerous reported studies. Our experimental results show that the spin diffusion length within iridium is 1.3 nm for resistivity of 250 nΩ.m, the spin mixing conductance 𝑔 𝑒𝑓𝑓 ↑↓ of the CoFeB/Ir interface is 30 nm -2 , and the spin Hall angle of iridium has the same sign than the one of platinum and is evaluated at 26% of the one of platinum. The value of the spin Hall angle found is 7.7% for Pt and 2% for Ir. These relevant parameters shall be useful to consider Ir in new concepts and devices combining spin-orbit torque and spin-transfer torque.

Rare‐Earth Permanent Magnet SmCo5 for Chiral Interfacial Spin‐Orbitronics

“…, the effective spin Hall angles of Pt/SmCo 5 /Ta, Pt/SmCo 5 /W and Pt/SmCo 5 /Ir can be obtained as 0.68, 0.53, and 0.29, respectively. These values are in agreement with the sum of the reported spin Hall angles of Pt (+0.02-0.15), [46,28] Ta (−0.15 to −0.25), [47,48] W (−0.18 to −0.36), [45,49] and Ir (0.01-0.02) [50,51] films, and are similar with the results from the Pt/ Co/Ta [44] and W/CoTb/Pt [45] trilayers.…”

“…and Ir (0.01~0.02) [50,51] films, and are similar with the results from the Pt/Co/Ta [44] and W/CoTb/Pt [45] trilayers.…”

Spin Pumping and Inverse Spin Hall Effect in Iridium Oxide

“…Recently Fache et al., reported spin pumping in CoFeB/Ir bilayers. [ 29 ] However, in our case we could not observe any ISHE voltage in CoFeB/Ir system. This might be due to the interface in the samples and/or the low power used in our set‐up.…”

Interplay between Spin‐Orbit Torques and Dzyaloshinskii‐Moriya Interactions in Ferrimagnetic Amorphous Alloys

“…Our ST‐FMR results in the Pt/CoGd/X series are consistent with the reported SHA values of W, Ta, and Ir in the literature. [ 25 , 26 , 27 , 43 ] Indeed, it was demonstrated that W and Ta have a much larger SHA than Pt and of opposite sign. [ 25 , 26 , 27 ] Due to the chirality of the spin‐orbit interactions at the top and bottom interface in Pt/CoGd/(W or Ta), spin currents from the two adjacent layers add up leading to a maximized SOT efficiency.…”