Role of Spin–Orbit Coupling on Ultrafast Spin Dynamics in Nonmagnet/Ferromagnet Heterostructures. Issue 8 (10th July 2022) - Panda, Surya Narayan
Abstract: Spin–orbit coupling (SOC), the interaction between spin and orbital angular momentum of electrons, is imperative to control magnetic properties of nonmagnet (NM)/ferromagnet (FM) heterostructures and design energy‐efficient and faster spin‐based devices. Here, femtosecond pulsed laser‐induced time‐resolved magneto‐optical Kerr effect magnetometry is employed to investigate magnetization dynamics in different NM/Co20 Fe60 B20 heterostructures, where the NM layer varies as Cu, Ta, W, Pt, Ta/Ru/Ta, and Si/SiO2 (no underlayer) that differ in SOC strength. It is observed that there is a systematic variation in ultrafast demagnetization time ( τ m ), fast remagnetization time ( τ r ), and Gilbert damping parameter ( α ) with the SOC strength of the underlayer and an inverse relationship between α and τ m, τ r is established due to the dominant contribution of spin current transport in ultrafast demagnetization and fast remagnetization processes. The spin pumping formalism estimates the effective spin‐mixing conductance ( G eff ) for different interfaces, which signifies that the high SOC strength of underlayers results in high G eff indicating more efficient transport of spin current through it. This study suggests that the SOC strength of the NM underlayer plays a significant role in controlling the ultrafast demagnetization process through interfacial spin current transport in a NM/FM heterostructure which can be beneficial for the development of ultrafast spintronics devices. Abstract : In this article, the authors investigate the effect of spin–orbit coupling on the ultrafast magnetization dynamics of nonmagnet/ferromagnet heterostructure by employing femtosecond pulsed laser‐induced TR‐MOKE magnetometry. It is observed that spin–orbit coupling plays a significant role in controlling the ultrafast demagnetization process through interfacial spin current transport which can be beneficial for the development of ultrafast spintronics devices.