  Spin-orbit torques, which utilize spin currents arising from the spin-orbit
coupling, offer a novel method to electrically switch the magnetization with
perpendicular anisotropy. However, the necessity of an external magnetic field
to achieve a deterministic switching is an obstacle for realizing practical
spin-orbit torque devices with all-electric operation. Here, we report a
field-free spin-orbit torque switching by exploiting the domain wall motion in
an anti-notched microwire with perpendicular anisotropy, which exhibits
multi-domain states stabilized by the domain wall surface tension. The
combination of spin-orbit torque, Dzyaloshinskii-Moriya interaction, and domain
wall surface tension induced geometrical pinning allows a deterministic control
of the domain wall and offers a novel method to achieve a field-free spin-orbit
torque switching. Our work demonstrates the proof of concept of a perpendicular
memory cell which can be readily adopted in a three-terminal magnetic memory.
