Robust Magnetic-Field-Free Perpendicular Magnetization Switching by Manipulating Spin Polarization Direction in RuO₂/[Pt/Co/Pt] Heterojunctions

Perpendicular magnetization switching by a magnetic-field-free, energy-efficient electrical approach has remained a great challenge. Here, we demonstrate the realization of robust magnetic-field-free perpendicular magnetization switching in the (101)RuO₂/[Pt/Co/Pt] heterojunction by manipulating the spin polarization direction. We proposed that the relative strength of out-of-plane spin currents with out-of-plane spin polarization <b>σ</b>_<i>z</i> and in-plane spin polarization <b>σ</b>_<i>y</i> can be effectively manipulated by tuning the nominal thickness of [Pt/Co/Pt] multilayers and the direction of applied electric current with respect to the RuO₂ crystal orientation. When the electric current is applied along RuO₂ [010] direction and the net spin current with spin polarization <b>σ</b>_<i>y</i> is canceled out, the "robust" perpendicular magnetization switching driven by pure <b>σ</b>_<i>z</i> is achieved in (101)RuO₂/[Pt/Co/Pt], where the term "robust" means that the switching polarity (counterclockwise) does not change and the switching ratio reduces very slowly with increasing magnitude of in-plane magnetic field <i>H</i>_<i>x</i> and/or <i>H</i>_<i>y</i> in a wide range of ±500 Oe. Our findings provide a technique to effectively manipulate the spin currents, which is beneficial for the investigation of antiferromagnetic spintronic devices with high magnetic field stability and reliable magnetization switching.