Energy efficiency analysis of spin–orbit torque MRAM using composition dependent resistivity and spin Hall angle in Pt/W multilayer structure

Current-induced magnetization switching through spin–orbit torque (SOT) enables low-energy and high-speed switching of magnetic memory (MRAM), positioning SOT-MRAM as a promising candidate for next-generation memory technology. As energy consumption in data computation has become a major challenge in the 21st century, significant efforts have been dedicated to developing energy-efficient memory devices. To optimize SOT-MRAM for energy efficiency, achieving a high spin Hall angle (SHA) has been regarded as essential, as a high SHA indicates efficient spin current generation. However, while previous studies have focused on increasing SHA, this has often led to increased resistivity, which may hinder overall energy efficiency in SOT-MRAM. We propose that resistivity is almost as important as SHA in determining the energy efficiency of SOT-MRAM. In this study, we analyze the effects of both SHA and resistivity in SOT channel materials, which can be modulated by adjusting the composition of Pt and W in Pt/W multilayers. We observed that varying the Pt and W compositions resulted in non-linear changes in both SHA and resistivity, suggesting that evaluating energy efficiency based solely on SHA may be misleading. Thus, we introduce a figure of merit, ξ=ρθSH2, which represents the combined impact of SHA and resistivity on SOT-MRAM energy efficiency. We hope that our findings reveal the importance of considering both SHA and resistivity in the development of energy-efficient SOT-MRAM.