Magnetic Domain-wall Tilting Mechanism during the Transition of Domain-wall Chiralilty

다국어 초록 (Multilingual Abstract)

Spin structure inside domain wall (DW) has attracted great attention due to its potential application on data storage or logic memory. Among terms affecting chirality of DW, Dzyaloshinskii-Moriya interaction (DMI) has been investigated in magnetic thin layer with perpendicular magnetization anisotropy. Based on such platform, most of experimental schemes have measured the chirality change under application of external in-plane field. By changing in-plane field, the direction of magnetization inside DW is changed, resulting in modification of chirality, DW energy, DW dynamics, etc. But those schemes have an assumption that DW is straightly placed across wire and only one variable, direction of the magnetization inside DW, is changed. Here, we propose generalized equation of equilibrium chirality with not only the degree of freedom of DW chirality (Ψ), but also the DW tilting angle (θ). With coordinate system in fig. 1, we numerically calculated equilibrium angle of Ψ and θ, giving a result of DW tilting in the transition regime of DW chirality (fig. 2). This result is counterintuitive in a sense that DW would not be tilted in transition regime as its energy is maximum at Ψ=0. Tilting angle of DW is maximum when in-plane field is applied as much as effective DMI field. Interestingly, the transition regime is widened as both Ψ and θ contribute to reduction of DW energy when in-plane field is changed. Additionally, we analytically calculated the critical field at which the DW starts and ends tilting. This study provides more realistic understanding of chirality and tilting mechanism by considering both contribution to DW energy.
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