Reduced Spin‐Orbit Torque Switching Current by Voltage‐Controlled Easy‐Cone States

• Published in: Advanced functional materials Vol. 32; no. 8
• Main Authors: Jeong, Jimin, Kang, Min‐Gu, Lee, Soogil, Kang, Jaimin, Lee, Kyung‐Jin, Park, Byong‐Guk
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.02.2022
• Subjects: Charge efficiency; Electric potential; Ferromagnetism; Heavy metals; Magnetic anisotropy; magnetic easy‐cone state; Materials science; Memory devices; multilevel memory; Power consumption; spin‐orbit torque; Switching; Torque; Voltage; voltage‐controlled magnetic anisotropy
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202107944

Spin‐orbit torque (SOT) promises fast and reliable switching of the perpendicular magnetization in spintronic devices, such as magnetic random‐access memory or spin logic devices. To apply the SOT technology to practical devices with low power consumption, it is necessary to reduce the switching current. To this end, most of the research to date in this area has focused on improving the charge‐to‐spin conversion efficiency in heavy metal/ferromagnet structures. In this study, it is reported that the SOT switching current is significantly reduced by modulating magnetic easy‐cone states through voltage‐controlled magnetic anisotropy (VCMA). The introduction of a thin Pt layer at the CoFeB/MgO interface enhances the VCMA effect, allowing a magnetic easy‐cone state of CoFeB to be formed and controlled by the gate voltage. As a result, the SOT switching current density is reduced by up to 50% when the easy‐cone angle is changed from 0° to 58°. Furthermore, the magnetic easy‐cone state is gradually modulated in a reversible and non‐volatile manner, facilitating multilevel spintronic devices. The reduction in spin‐orbit torque (SOT) switching current by the voltage‐controlled magnetic easy‐cone state is demonstrated. In Ta/CoFeB/Pt/MgO structures, the easy‐cone state is efficiently modulated by the gate voltage, resulting in the reduction of the SOT switching current by up to 50%. The reversible and nonvolatile nature of the voltage‐controlled easy‐cone state facilitates multilevel spintronic devices.