  Current-induced magnetization switching by spin-orbit torque (SOT) holds
considerable promise for next generation ultralow-power memory and logic
applications. In most cases, generation of spin-orbit torques has relied on an
external injection of out-of-plane spin currents into the magnetic layer, while
an external magnetic field along the electric current direction is generally
required for realizing deterministic switching by SOT. Here, we report
deterministic current-induced SOT full magnetization switching by lateral
spin-orbit torque in zero external magnetic field. The Pt/Co/Pt magnetic
structure was locally annealed by a laser track along the in-plane current
direction, resulting in a lateral Pt gradient within the ferromagnetic layer,
as confirmed by microstructure and chemical composition analysis. In zero
magnetic field, the direction of the deterministic current-induced
magnetization switching depends on the location of the laser track, but shows
no dependence on the net polarization of external out-of-plane spin currents.
From the behavior under external magnetic fields, we identify two independent
mechanisms giving rise to SOT, i.e. the lateral Pt-Co asymmetry as well as
out-of-plane injected spin currents, where the polarization and the magnitude
of the SOT in the former case depends on the relative location and the laser
power of the annealing track. Our results demonstrate an efficient field-free
deterministic full magnetization switching scheme, without requiring
out-of-plane spin current injection or complex external stack structures.
