Flexible magnetic sensors combine the mechanical deformability of flexible electronics with the precision of non-contact and vector magnetic detection, presenting broad application potential in humanoid robotics, healthcare monitoring, and virtual reality.

However, strain-induced instability during fabrication and operation has long hindered their practical implementation. In real-world scenarios, flexible electronic devices frequently undergo non-uniform strain, a more complex state than idealized uniform deformation.

In a study recently published in Advanced Materials, researchers from the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences have revealed how strain gradients influence magnetic properties. Understanding this mechanism is key to achieving stable and reliable performance in next-generation flexible magnetic devices.

The researchers incorporated microscale wrinkled structures into sputtered Pt/Co/Ta magnetic films, producing tunable strain gradients with varying magnitudes and directions.

Using magnetic force microscopy, the team observed that skyrmion density and size vary synchronously with the strain gradient, thereby affecting the magnetic properties of the device. In regions with negative strain gradients, skyrmions exhibit greater stability, with higher densities and larger sizes. In contrast, skyrmion stability is diminished in regions with positive strain gradients.

By tuning in-plane strain gradients, the researchers were able to continuously adjust skyrmion density from 1 to 13 μm^-2 and skyrmion size from 85 to 133 nm. Notably, the modulation efficiency achieved via strain gradients surpasses that under uniform strain conditions.

Micromagnetic simulations suggest that these effects originate from the strain-gradient-induced breaking of local inversion symmetry, which effectively modulates the interfacial Dzyaloshinskii–Moriya interaction. This strain-gradient modulation strategy exhibits excellent reversibility and cycling stability, retaining consistent performance after repeated stretching–release cycles while being applicable to other ferromagnetic multilayer systems.

This work offers new insights into the modulation mechanisms of magnetic materials under complex strain conditions, providing a new route for developing flexible magnetic sensors with improved strain stability.