Thickness dependence of spin–orbit torques in Pt/Co structures on epitaxial substrates

Abstract

We investigate the Pt thickness dependence of spin–orbit torques (SOTs) in Co/Pt layers grown on single crystalline SrTiO3 and LaAlO3 and amorphous SiO2 substrates. We measure the SOT-induced effective damping-like fields and spin Hall magnetoresistances of the Co/Pt (tPt) samples, where tPt varies from 0.5 to 5.5 nm. We find that the Co/Pt layers grown on the single crystalline substrates show weaker thickness dependence of the SOT than the samples on the SiO2 substrate, which cannot be explained by the conventional bulk spin Hall effect in the Pt layer. This indicates that there is a non-negligible interfacial SOT originating from the Pt/substrate interface, which is more pronounced for thinner Pt. These results provide a way to design SOT material structures with enhanced SOT efficiency by incorporating interfacial SOT.

Thickness Dependence of Interface‐Generated Spin Currents in Ferromagnet/Ti/CoFeB Trilayers

“…[12][13][14][15][16][17][18][19][20][21] The latter generates a spin density at the NM/FM interfaces with inversion asymmetry. [22][23][24][25][26][27][28][29][30] Both mechanisms induce spin accumulations, which exert spin torques and manipulate the magnetization direction of the FM layer.…”

“…[12][13][14][15][16][17][18][19][20][21] The latter generates a spin density at the NM/FM interfaces with inversion asymmetry. [22][23][24][25][26][27][28][29][30] Both mechanisms induce spin accumulations, which exert spin torques and manipulate the magnetization direction of the FM layer.Recent studies have revealed another spin current generation mechanism. In the so-called interface-generated spin current, [31][32][33][34][35] the FM/NM interface gives rise to sizable spin currents.…”