Current-induced DW velocity in freestanding HM/FM heterostructures (with and without MgO buffer layer) and in as-deposited HM/FM heterostructures (on MgO substrates) with different Pt thicknesses marked in the figure. Different colors represent different samples: Violet, blue and cyan for freestanding samples without MgO buffer layers; dark and light green for freestanding samples with a MgO buffer; dark red and red for as-deposited samples on MgO. The black stars represent data from Ref.[26], corresponding to devices with a 50 Å Pt layer and a MgO buffer layer. Link to the Creative Commons License:http://creativecommons.org/licenses/by/4.0/. Insets in e: typical Kerr images of DW motion in response to a series of injected 10-ns-long current pulses (J= 1.87 × 108A cm−2) composed of two pulses in freestanding HM/FM heterostructures without a MgO buffer layer and with 25 Å Pt transferred onto a sapphire substrate. The bright and dark regions correspond to down (⊗ or ↓) and up (⊙ or ↑) domains. The error bars in e represent a standard deviation.
