Figure 4: Helicity-dependent magnetic domain wall depinning. | Nature Communications

Figure 4: Helicity-dependent magnetic domain wall depinning.

From: Inertial displacement of a domain wall excited by ultra-short circularly polarized laser pulses

Figure 4

(a) Experiment: To obtain BDP, we first saturate the magnetization in a strong negative field. Then, a reversed domain is nucleated and a DW is positioned at the cross entrance. The LP spot is now focused to its ‘start’ position 10 μm away from the initial DW location within the reversed domain. Subsequently, the spot is swept by 20 μm along the bar crossing the initial DW position with a velocity of 2 μm ms−1. Starting from a small negative applied field of BA=−0.1 mT, DW depinning is inferred from AHE measurements and differential MOKE micrographs taken after the laser spot sweep at constant BA. If the DW is still located at the cross entrance, BA is increased by +0.025 mT followed by another laser spot sweep and subsequent AHE and MOKE detection. This procedure is repeated with stepwise increased BA until DW depinning is detected. Each individual data-point of BDP is obtained as the average from five independent depinning field measurements. The error bars correspond to the maximal observed scatter of BDP around the corresponding mean values. (b) Depinning field BDP as a function of LP energy density for circularly left (red), linearly (black) and circularly right (blue) polarized light up to the highest LP energy density where the temperature increase due to LP heating does not exceed the Curie temperature of the magnetic film. Depinning at zero applied field is only observed if the oSTT is generated by σ+-polarized LPs. (c) Final domain configuration after laser sweeps with an applied field larger than propagation field BPR and (d) at zero or small negative applied magnetic field.

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