Tunable Magnetoelastic Response in Flexible Magnetic Nanofilms via Fragmentation Control and Multilayer Design

We report a strategy to tailor the magnetoelastic response of flexible ferromagnetic thin films by engineering their mechanical fragmentation through material selection and multilayer design. Using in situ magneto-optical Kerr effect (MOKE) magnetometry combined with uniaxial tensile testing and optical imaging, we explore how ductile and brittle behaviors influence the evolution of magnetic anisotropy and coercivity under strain. Comparative studies of Co monolayers, Co/W, Co/Au bilayers, and Ni films reveal that the nature of the underlayer and the film thickness critically determine the fragmentation pattern, the onset of buckling, and the resulting magnetoelastic field. We show that in brittle systems, abrupt stress redistributions caused by multicracking and buckling lead to sharp, nonreversible changes in magnetic properties, while ductile systems exhibit gradual, tunable responses due to progressive plastic deformation. These results highlight a design framework for controlling magneto-mechanical functionality in flexible magnetic systems, offering pathways for reconfigurable magnetic devices and strain-adaptive electronics.