Enhancing damping-like efficiency by low-energy mixed ions bombardment

Abstract

Pursuing enhanced spin–orbit torque (SOT) has become a significant focus for achieving energy-efficient spintronics devices. Researchers have explored different materials, layer engineering, and various post-deposition modification methods to realize higher SOT. Here, we have utilized the bombardment of mixed ions (Ar+ and He+ in various ratios) with 0.6 kV bias voltage to enhance the SOT efficiency in a Pt/Co/W stack. The bombardment modifies the physical properties (magnetic, electric, and structural) due to cascade collision, knocking off atoms (from the surface), and ion implantation. The increased percentage of He+ suppresses the drastic behavior of cascade collisions, and hence, the properties are tunable by changing the gas ratio. We exploited this behavior to design a material stack with enhanced SOT efficiency. We fabricated Hall bars to quantify SOT and observed a 4.5× increase in the effective damping-like efficiency. The efficiency and switching current density in the stack could be tuned by the variation of Ar:He ion ratio and the exposure duration. This study offers an easy route to tune the energy efficiency of spin devices, contributing to the advancement of next-generation spintronics.

Charge–spin interconversion in nitrogen sputtered Pt via extrinsic spin Hall effect

“…Side-jump scattering has been observed in alloys such as AuTa [17], CuPt [18], in adding lighter impurities such as oxygen (O) and nitrogen (N) in host Pt via ion-implantation [19,20], and by introducing SrTiO 3 into Pt by sputtering [21]. Introduction of lighter impurities such as O and N in Pt, Ta by using sputtering [22,23], O in Pt by plasma irradiation [24], and Ar + and He + in Pt/Co/W stack [25] have also been exploited to enhance the SHE, but the quest to understand the underlying SHE mechanism remains challenging. Moreover, for the implementation of practical device applications, such as SOT magnetic random-access memory (SOT-MRAM), a trade-off between the θ SH and longitudinal resistivity, ρ xx is critical [19].…”