Figure 3. Conversion between a skyrmion and a bimeron.

The top panels show the snapshots of the magnetization configuration at six selected times corresponding to the vertical lines in the middle and bottom panels; the middle panels show the time evolution of the average spin components m_x, m_y, m_z; the bottom panels show the time evolution of the skyrmion number Q_s. (a), Conversion between a skyrmion and an anti-bimeron: the D in the sample is 3.5 mJ m⁻²; the anisotropy K is 0.8 MJ m⁻³ in the input side and −0.8 MJ m⁻³ in the output side, while a gradient transition from 0.8 MJ m⁻³ to −0.8 MJ m⁻³ is set in the narrow channel, i.e. the plane of the input side is a hard plane, while the plane of the output side is an easy plane. The initial background magnetization of the input side points +z, while it is mostly aligned along −x direction in the output side; a current density of 9 × 10¹² A m⁻² (the value is of the input or output side, similarly hereinafter) is applied along −x direction for 0 ns < t < 0.17 ns followed by a relaxation without applying any current until t = 1 ns. (b), Conversion between a skyrmion and a bimeron: the D is 3.5 mJ m⁻²; the profile of the anisotropy is the same as that in a. The initial background magnetization of the input side points +z, while it is mostly aligned along +x direction in the right output side; a current density of 10 × 10¹² A m⁻² is applied along −x direction for 0 ns < t < 0.15 ns followed by a relaxation until t = 1 ns.