  Magnetic random-access memory (MRAM) driven by spin-transfer torque (STT) is
a major contender for future memory applications. The energy dissipation
involved in writing remains problematic, even with the advent of more efficient
perpendicular magnetic anisotropy (PMA) devices. A promising alternative
switching mechanism employs spin-orbit torques and the spin-Hall effect (SHE)
in particular, but additional symmetry breaking is required to achieve
deterministic switching in PMA devices. Currently used methods rely on in-plane
magnetic fields or anisotropy gradients, which are not suitable for practical
applications. Here, we interface the magnetic layer with an anti-ferromagnetic
material. An in-plane exchange bias (EB) is created, and shown to enable
field-free SHE-driven magnetization reversal of a perpendicularly magnetized
Pt/Co/IrMn structure. Aside from the potential technological implications, our
experiment provides additional insight into the local spin structure at the
ferromagnetic/anti-ferromagnetic interface.
