Domain Walls in A1-FePt

The majority of early work on DW motion focused on permalloy (NiFe) nanowires with low in-plane anisotropy (~ 2  104 erg cm-3). We investigated the DW dynamics in chemically disordered in-plane A1-Fe57Pt43 (10 nm thick), with a larger anisotropy of~ 6  105 erg cm-3. Translation of a 180° vortex domain wall was observed at an applied field of Hx ≥ 40 Oe, and the domain wall moved to the end of the arc at Hx = 100 Oe. Domain wall displacement was observed with low pulsed current densities of (2.5 – 5.0)  1011 A m-2 at zero magnetic field, but DW velocities were small at (7 – 180)  10-4 m s-1. A field assisted spin transfer torque (STT) led to further displacement compared to current alone, with the DW travelling at least 1.8 μm away from the centre to the end of the arc. The strong spin orbit scattering and poor spin polarization are believed to limit efficient spin transfer driven DW motion in A1-FePt.