Dipolar field-assisted domain wall depinning in trilayer structures

Depinning of dipolar-coupled domain walls (DWs) in 3D permalloy/non-magnetic/permalloy trilayers from notches was investigated using micromagnetic simulation.Due to the coupling, DWs in the top and bottom layers exhibited opposing magnetizations, resulting in either clockwise (CW) or anti-clockwise (ACW) circulation of magnetization. When propagating the DWs toward a notch positioned on one side of the wire, three distinct phases were observed: no depinning(P0), only one wall depinning (P1) or both walls depinning (P2). Depinning thresholds in the trilayer system were lower than in isolated layers due to the transverse component of the dipolar-coupled field between coupled DWs. While theP0-P1 phase boundary was unaffected by stackingorder, theP1-P2transition required up to 170% higher fields for CW walls than ACW walls, due to the flux closure causing slight DW offsets and selecting the magnetization of the leading wall. This study demonstrates how dipolar-coupled stray field shape the depinning field, revealing unique 3D properties beyond those of individual layers.