The optimized memristor performance by utilizing the constrained domain wall motion in Pt/Co–Tb/Ta structure

Abstract

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.

Field-Free Spin–Orbit Torque-Induced Magnetization Switching in the IrMn/CoTb Bilayers with a Spontaneous In-Plane Exchange Bias

“…Similar incomplete switching occurs in other samples with different x . This is possibly due to the CoTb demagnetizing resulting from the thermal effect after applying current pulses, similar to those in previous reports. , As shown in Figure S2 in the Supporting Information, the AHE loop becomes more and more slanted while the H c decreases obviously with increasing I p from 5 to 15 mA, indicating that the PMA of the CoTb layer reduces significantly with increasing I p , which verifies the pulse current-produced thermal effect.…”

“…After I p exceeds about −28 mA, the magnetization reversal in the central parts has finished while it begins to happen at the cross parts due to inhomogeneous current density distribution or current shunting effect. 17,32 Note that this reversal process has not been fully accomplished even at I p = −35 mA, consistent with not up to 100% switching fraction in the present devices. A similar magnetization reversal process can be also observed with increasing the amplitude of the positive current after the device was initialized by I p = −35 mA, as shown in Figure S5, Supporting Information.…”

“…This is possibly due to the CoTb demagnetizing resulting from the thermal effect after applying current pulses, similar to those in previous reports. 28,32 As shown in Figure S2 in the Supporting Information, the AHE loop becomes more and more slanted while the H c decreases obviously with increasing I p from 5 to 15 mA, indicating that the PMA of the CoTb layer reduces significantly with increasing I p , which verifies the pulse currentproduced thermal effect. Similar measurements were performed on another sample (the FiM composition is Co 0.78 Tb 0.22 ) with negative spontaneous IEB (H eb = −151 Oe), and the results are shown in Figure S3, Supporting Information.…”

“…Up to now, although there have been some studies demonstrating SOT-driven magnetization switching in single RE-TM layers or heavy metal (HM)/RE-TM bilayers, ,,− few results of field-free magnetic switching were reported in RE-TM systems. Guo et al first reported that this task could be accomplished in the Co/Ti/CoTb trilayers, in which an out-of-plane effective field acting on the CoTb layer is produced due to the spin–orbit precession effect at the NM/FM interface .…”

Granular Magnetization Switching in Pt/Co/Ti Structure with HfOx Insertion for In-Memory Computing Applications

“…The magnetization reversal based on domain nucleation provides gradual switching behavior and paves an alternative solution to achieve the multiple resistance states. , In the early stages, Fukami et al introduced the concept of multidomain behavior in the PtMn/(Co/Ni) 2 system, which relates to the exchange bias for high DW propagation energy caused by a magnetic field annealing process at 300 °C . Recently, Zhou et al demonstrated the DW nucleation switching in the L1 1 -CuPt/CoPt bilayer, which requires high-temperature epitaxial deposition on SrTiO 3 (111) substrate .…”