Giant spin-orbit torque induced by spin Hall effect in amorphous Pt(P) alloys

Abstract We report a giant spin-orbit torque (SOT) induced by spin Hall effect (SHE) in amorphous Pt(P) alloys, which is confirmed by magnetization switching and spin torque-ferromagnetic resonance measurements. Pt(P) is fabricated by ion-implantation technique using energies from 10 to 30 keV with doses ranging from 2.5 × 10 ¹⁶ to 10 × 10 ¹⁶ ions/cm ² . The P-ion implantation process causes distortion and defects in the fcc structure of the as-deposited Pt layer and changes it to an amorphous structure as the accelerating energy as well as the dose increases, leading to a decrease in the electrical conductivity. However, we can obtain a higher spin Hall conductivity, $${\sigma }_{{\rm{xy}}}^{{\rm{SH}}}$$ of $$3.62\times {10}³\frac{\hslash }{2e}{\Omega }^-1{\mathrm{cm}}^-1$$ for Pt(P) as compared to that of $$1.03\times {10}³\frac{\hslash }{2e}{\Omega }^-1{\mathrm{cm}}^-1$$ for pure Pt. The spin Hall efficiency, $${\theta }_{{\rm{SH}}}$$ is drastically increased up to 1.17 for Pt(P) with 30 keV energy and dose of 7.5 × 10 ¹⁶ ions/cm ² . We also observe a significant reduction in the critical switching current density, $${J}_{{\rm{sw}}}$$ of the SOT magnetization switching from 1.5 × 10 ¹¹ A/m ² for pure Pt to 3.0 × 10 ¹⁰ A/m ² for Pt(P). Such a giant SHE can reduce the power consumption to control the magnetization by using SOT, and therefore our findings may provide an alternate path to enhance $${\theta }_{{\rm{SH}}}$$ by using amorphous materials with a variety of elements, beyond crystalline solids.