Flexible magnetoelectronic systems are emerging as key technologies for adapting to complex geometries, with promising applications in confined environments and flexible displays. These systems leverage polymers, which are lighter and more cost-effective than silicon. Understanding the interactions between mechanical deformation and magnetic properties is critical: magnetic anisotropy dominates at low strains, while at high strains, microscopic damage—such as fragmentation and decohesion—plays a pivotal role [1-2]. Despite their importance, the effects of thin-film fragmentation on magnetic properties under biaxial tension remain underexplored. To address this gap, we investigated model flexible magnetic systems using in situ techniques capable of inducing significant deformations (up to 10%) while characterizing magnetic behavior. A custom tensile device was developed for use within the air gap of an electromagnet, along with a magneto-optical Kerr effect (MOKE) magnetometer. Additionally, we integrated a MOKE magnetometer into the DiffAbs beamline at the Soleil synchrotron for synchrotron-based studies. Our work examines the relationships between stress distribution, fragment size effects, and magnetic response, shedding light on the mechanisms driving these phenomena. This research advances the understanding of flexible magnetoelectronic materials and their behavior under mechanical stress, paving the way for innovative applications in flexible electronics.