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

Abstract

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 σz and in-plane spin polarization σy 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 σy is canceled out, the "robust" perpendicular magnetization switching driven by pure σz 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 Hx and/or Hy 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.