Abstract
Spin–orbit torque facilitates efficient magnetisation switching via an in-plane current in perpendicularly magnetised heavy-metal/ferromagnet heterostructures. The efficiency of spin–orbit-torque-induced switching is determined by the charge-to-spin conversion arising from either bulk or interfacial spin–orbit interactions or both. Here, we demonstrate that the spin–orbit torque and the resultant switching efficiency in Pt/CoFeB systems are significantly enhanced by an interfacial modification involving Ti insertion between the Pt and CoFeB layers. Spin pumping and X-ray magnetic circular dichroism experiments reveal that this enhancement is due to an additional interface-generated spin current of the non-magnetic interface and/or improved spin transparency achieved by suppressing the proximity-induced moment in the Pt layer. Our results demonstrate that interface engineering affords an effective approach to improve spin–orbit torque and thereby magnetisation switching efficiency.
Highlights
spin–orbit torque (SOT) in heavy metal (HM)/ferromagnet (FM)/oxide heterostructures arises from the spin current induced by a charge current via the spin Hall effect (SHE) in the HM and/or the interfacial spin–orbit coupling (ISOC) effect at HM/FM interfaces
Our results demonstrate that interface engineering affords an effective approach to improve spin–orbit torque and thereby magnetisation switching efficiency
SOT in heavy metal (HM)/ferromagnet (FM)/oxide heterostructures arises from the spin current induced by a charge current via the spin Hall effect (SHE) in the HM and/or the interfacial spin–orbit coupling (ISOC) effect at HM/FM interfaces
Summary
SOT in heavy metal (HM)/ferromagnet (FM)/oxide heterostructures arises from the spin current induced by a charge current via the spin Hall effect (SHE) in the HM and/or the interfacial spin–orbit coupling (ISOC) effect at HM/FM interfaces. During scanning around the Pt L3 edge, the helicity of the X-rays was reversed at 0.5 Hz. We first study the effect of the interfacial modification upon Ti insertion on SOT-induced magnetisation switching using Pt(5 nm)/Ti(tTi)/CoFeB(1 nm)/MgO Hall bar structures, where tTi is varied from 0 to 3 nm [Fig. 1(a)].
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