  Deterministic magnetization switching using spin-orbit torque (SOT) has
recently emerged as an efficient means to electrically control the magnetic
state of ultrathin magnets. The SOT switching still lacks in oscillatory
switching characteristics over time, therefore, it is limited to bipolar
operation where a change in polarity of the applied current or field is
required for bistable switching. The coherent rotation based oscillatory
switching schemes cannot be applied to SOT because the SOT switching occurs
through expansion of magnetic domains. Here, we experimentally achieve
oscillatory switching in incoherent SOT process by controlling domain wall
dynamics. We find that a large field-like component can dynamically influence
the domain wall chirality which determines the direction of SOT switching.
Consequently, under nanosecond current pulses, the magnetization switches
alternatively between the two stable states. By utilizing this oscillatory
switching behavior we demonstrate a unipolar deterministic SOT switching scheme
by controlling the current pulse duration.
