Tuning magnonic band structures through substrate elasticity

Strain provides an energy-efficient route to reconfiguring magnonic functionalities, yet the physical mechanisms by which strain reshapes spin-wave spectra in magnonic crystals supported on deformable substrates remain insufficiently understood. Here, we investigate how the elastic modulus of the substrate governs strain-induced modifications of magnonic band structures in two-dimensional arrays of CoFeB nanomagnets, using a numerical multiphysics approach that couples magnetization dynamics with solid mechanics. We show that substrates with higher elastic modulus transmit a finite strain into the nanomagnets, giving rise to strong magnetoelastic fields that dominate the band evolution, whereas highly compliant substrates accommodate most of the applied strain within the substrate itself, concentrating strain between elements and primarily modifying dipolar interactions. As a result, for identical applied strains, substrates such as PDMS and Kapton lead to qualitatively different magnonic band structures due to their strongly contrasted strain-transfer characteristics. These findings establish substrate elasticity as a key design parameter for engineering strain-tunable and mechanically reconfigurable magnonic crystals.