Pulse-width and thermal effects on field-free memristive spin-orbit torque switching

Abstract

Spin-orbit torque (SOT) has been demonstrated to manipulate the magnetization in various types of heterostructures. Besides the conventional current-induced SOT switching with the assistance of in-plane bias field, field-free SOT switching and memristive SOT switching have also drawn lots of interests due to the possible applications in commercial magnetic random access memory (MRAM) and neuromorphic computing devices. To further decrease power consumption in such devices, most works commit to enhance the SOT efficiency. However, the thermal stability of device is also essential for reliable applications. Especially when SOT devices are integrated with CMOS that the thermal dissipations from transistors can cause significant increase of ambient temperature.In this work, we systematically investigate the SOT efficiencies, thermal stability factors (Δ), and memristive SOT switching behaviors of a standard W/CoFeB/MgO device and a field-free CoFeB/W/CoFeB/MgO device. In both samples, the SOT efficacies are characterized to be constant from 25 °C (298 K) to 80 °C (353 K), where the thermal stability factors (Δ) are slightly degraded as increasing the temperature. The memristive SOT switching behaviors in both systems with various pulse-widths and temperatures are also examined.1 The memristive switching windows are found to shrink at elevated temperatures, which poses the potential challenge of employing SOT devices in realistic neuromorphic applications. Our results suggest that, although the SOT efficacy is robust against thermal effects, the reduction of Δ at elevated temperatures could be detrimental to standard memory as well as neuromorphic (memristive) device applications.2 **