Current-induced magnetization switching in compensated ferrimagnetic materials by the spin–orbit torque (SOT) effect is promising for the next generation information storage devices. In this work, we report the current-induced deterministic field-free magnetization switching of the perpendicular Tb-Co ferrimagnet layer in a Co/Ti/Tb-Co trilayers. We found that the switching proportion and polarity of the Tb-Co ferrimagnet depend on the magnetization direction of the in-plane Co layer. The switching process revealed by magneto-optical Kerr microscope imaging further confirmed the current-induced field-free switching of the Tb-Co layer. We also demonstrated the large SOT effective field and the perpendicular effective field acting on the Tb-Co layer, by utilizing the second harmonic voltage measurement and the current-induced loop shift method. The large interfacial SOT efficiency and deterministic field-free magnetization switching in the trilayers structure may accelerate the application of ferrimagnet in SOT memory devices.
Spintronic devices can realize multilevel state storage and mimic the properties of the synapse, which enables their potential application in the field of artificial neural networks. In this paper, we demonstrate the existence of a large intermediate transition zone in current-induced magnetization switching curves of Pt/Co–Tb/Ta structures, and the number of states in the transition zone that can be manipulated by changing the Co content. The magneto-optical Kerr microscope imaging indicates that this property is related to the constrained domain wall motion in the Co–Tb films with large Co content. We also demonstrate the multilevel state storage properties of the sample by applying a sequence of current pulses. The synaptic plasticity behaviors were mimicked in these samples through regulating the value of Hall resistance by current pulses. The constrained domain wall motion supplies a simple but effective way to achieve multilevel state storage and show potential applications in neuromorphic computing.
Although transition metal (TM)-rare earth (RE) alloy film has potential application as an information storage medium in spintronic devices, study of the physical mechanism and microscopic process for the current-induced magnetization switching by spin–orbit torque (SOT) in TM-RE is still inadequate. In this work, we investigated the SOT effect and its driven magnetization switching in Pt/Co–Tb/Ta structures with various Co–Tb compositions. The results show that the current-induced SOT effective fields follow 1/Ms law near the compensation composition in this structure. Because of the large SOT effective field and the low coercivity for the Co–Tb layer near the compensation composition, the current-induced magnetization switching with a threshold current density as low as 1010 A/m2 was achieved in the system. The direct Kerr imaging on the switching process verifies two different current-induced switching mechanisms in the Pt/Co–Tb/Ta system.
We investigate a current-induced magnetization reversal process mediated by spin-orbit torque (SOT) in Ta/Pt/(Co/Ni) n Co/Ta multilayers experimentally and by micromagnetic simulation. Experimental results show that the current-induced magnetization reversal in these samples is completed by nucleation and subsequent domain wall (DW) propagation. For samples with a small number (n) of Co/Ni bi-layers, which show strong Dzyaloshinskii-Moriya interaction (DMI), when the in-plane magnetic field (H x ) is weaker than a critical value, the tilted DWs form in the final stabilized state, corresponding to a partial magnetization reversal. Since H x is close to the DMI effective field, the domains expand asymmetrically to semicircular areas, finally resulting in complete magnetization reversal. For the sample with large n and weak DMI, the reversed domains grow obliquely along a special orientation, which varies with the magnitude of H x . These experimental phenomena are well reproduced by micromagnetic simulation after taking into account the SOT effect and the DMI-modulated magnetic moment distribution in the DW. The agreement betweenexperimental observation and micromagnetic simulation suggests that the current-induced magnetization reversal process in the Ta/Pt/[Co/Ni] n Co/Ta system can be well understood within the framework of SOT and the DMI scenario.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.