Emergent magnetic behavior in large-scale 3D arrays of multisegmented nanowires with disk-shaped magnetic segments

Understanding the magnetic behavior of multisegmented nanowires (MNWs) is essential for developing three-dimensional spintronic devices. However, the relationship between magnetic segment shape, intra-and inter-wire interactions, and magnetization reversal in large MNW arrays is not sufficiently understood. Here, we fabricate arrays of NiFe/Cu MNWs using pulsed electrochemical deposition within porous anodic alumina templates featuring 40 nm pore diameters. The MNWs consist of disk-shaped NiFe segments (18 +/- 2 nm thick) separated by Cu spacers with thicknesses of 4 and 12 nm. Increasing the number of magnetic segments from 50 to 400 segments, we showed that stronger inter-wire interactions suppress out-of-plane (OOP) squareness, while coercivity remains nearly constant. Experimental results combined with micromagnetic simulations reveal that, in large-scale arrays, a cooperative effect between weak intra-wire coupling (thick spacers) and strong inter-wire interactions (high segment number) induces a switch of the easy magnetization axis from parallel to perpendicular relative to the wire axis for MNWs with segment numbers exceeding a critical threshold of 100. Micromagnetic simulations indicated the magnetization reversal involving multiple mechanisms: curling nucleation preceded OOP coherent rotation, whereas in-plane reversal predominantly occurs via coherent rotation regardless of spacer thickness. Angular-dependent measurements confirm a transition from curling to coherent rotation with increasing angle for strongly coupled (4 nm spacer) MNWs, while 12 nm spacer MNWs exhibit coherent rotation across all angles. Remarkably, reversal modes are unaffected by segment number for both spacer thicknesses, providing insights into anisotropy engineering in MNW-based spintronic architectures.