Initialization-Free and Magnetic Field-Free Spin–Orbit p-Bits with Backhopping-like Magnetization Switching for Probabilistic Applications
Ruizhi Ren, Yi Cao, Chao Wang, Yicheng Guan, Shuai Liu, Lijin Wang, Zeting Du, Chun Feng, Zelalem Abebe Bekele, Xiukai Lan, Nan Zhang, Guang Yang, Le Wang, Baohe Li, Yong Hu, Yan Liu, S. Parkin, Kaiyou Wang, Guanghua Yu
Abstract
Probabilistic bits (p-bits) with thermal- and spin torque-induced nondeterministic magnetization switching are promising candidates for performing probabilistic computing. Previously reported spin torque p-bits include volatile low-energy barrier nanomagnets (LBNMs) with spontaneously fluctuating magnetizations and initialization-necessary nonvolatile magnets. However, initialization-free nonvolatile spin torque p-bits are still lacking. Here, we demonstrate moderately thermal stable spin-orbit torque (SOT) p-bits with non-consecutively deposited Pt//Pt/Co/Pt stacks. Backhopping-like (BH) magnetization switching with a wide range current-tunable probability of final up and down magnetization states from 0% to 100% was achieved, regardless of the initial magnetization state, which was attributed to the interplay of SOT and thermal contributions. Integer factorization using such BH-SOT p-bits in zero magnetic field was demonstrated at times that are significantly shorter than those of existing nonvolatile STT or volatile LBNMs p-bits. Our realization of initialization-free and magnetic field-free moderately thermally stable BH-SOT p-bits opens up a new perspective for probabilistic spintronic applications.