Fig. 5. Controllable switching polarity of the field-free SOT switching.

a In-plane hysteresis loops of the IrMn/Co/Ru/CoPt heterojunctions measured by magnetic optical Kerr effect. The initial state is set by applying a positive current pulse of $+14\mathrm{mA}$ under $H_{\mathrm{x}}=-400\mathrm{Oe}$. Then the initial state is reset by a single current pulse with various amplitude and direction under $H_{\mathrm{x}}=+400\mathrm{Oe}$. b The field-free clockwise switching in the initial state. c The field-free counterclockwise switching after reset by applying a positive current pulse of $+14\mathrm{mA}$ under $H_{\mathrm{x}}=400\mathrm{Oe}$. The insets show the schematic magnetic configuration of Co layer and CoPt layer.