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.