2018/10/24 by Jiawei Yu, Do Bang, Rahul Mishra +16 · 134 citations
Materials Science · Physics and Astronomy · #Coherence length #Condensed matter physics #Ferrimagnetism #Ferromagnetic resonance #Ferromagnetism #Heusler alloys: electronic and magnetic properties #Magnetic field #Magnetic properties of thin films #Magnetization #Materials science #Physics #Quantum mechanics #Spin (aerodynamics) #Spintronics #Torque #ZnO doping and properties #cond-mat.mtrl-sci
paper · pdf · doi:10.1038/s41563-018-0236-9
published in Nature Materials 18(1), 29-34 (Nature Portfolio)
arxiv created 2018/10/24 · openalex publication_date 2018/11/23 · arxiv updated 2018/12/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Ferromagnetic spintronics has been a main focus as it offers non-volatile memory and logic applications through current-induced spin-transfer torques. Enabling wider applications of such magnetic devices requires a lower switching current for a smaller cell while keeping the thermal stability of magnetic cells for non-volatility. As the cell size reduces, however, it becomes extremely difficult to meet this requirement with ferromagnets because spin-transfer torque for ferromagnets is a surface torque due to rapid spin dephasing, leading to the 1/ferromagnet-thickness dependence of the spin-torque efficiency. Requirement of a larger switching current for a thicker and thus more thermally stable ferromagnetic cell is the fundamental obstacle for high-density non-volatile applications with ferromagnets. Theories predicted that antiferromagnets have a long spin coherence length due to the staggered spin order on an atomic scale, thereby resolving the above fundamental limitation. Despite several spin-torque experiments on antiferromagnets and ferrimagnetic alloys, this prediction has remained unexplored. Here we report a long spin coherence length and associated bulk-like-torque characteristic in an antiferromagnetically coupled ferrimagnetic multilayer. We find that a transverse spin current can pass through > 10 nm-thick ferrimagnetic Co/Tb multilayers whereas it is entirely absorbed by 1 nm-thick ferromagnetic Co/Ni multilayer. We also find that the switching efficiency of Co/Tb multilayers partially reflects a bulk-like-torque characteristic as it increases with the ferrimagnet-thickness up to 8 nm and then decreases, in clear contrast to 1/thickness-dependence of Co/Ni multilayers. Our results on antiferromagnetically coupled systems will invigorate researches towards energy-efficient spintronic technologies.