Different correlations between spin Hall angle measured by the 2nd harmonic method and by the critical current density due to dimension effect in W/Ta multilayers

Abstract

We obtain varying spin Hall angle (θSH, 2nd) values measured by the 2nd harmonic methods in W/Ta multilayers system with relatively low resistivity by doping Ta into mixed-phase W with both α and β phases (α-W, β-W). A remarkably increased value of θSH, 2nd is observed from 0.04 (W) to 0.47 (W1/Ta0.25), which is attributed to the formation of β-W3Ta. The influences of θSH, 2nd on the critical switching current density (Jc) were investigated by the spin Hall angle (θSH,Jc). It is found that the θSH,Jc has strong correlations with θSH, 2nd in large dimension samples, indicating the Jc can be lowered by the enhancement of θSH, 2nd. This correlation gradually disappears in smaller dimension samples, due to the pinning effect and domain wall (DW) surface tension, which are confirmed by microsimulations.