Strain evolution of spin-wave in BiFeO₃ thin film

BiFeO₃ is one of the most famous multiferroic systems, due to its strong magneto‐electric coupling at room temperature promising large potential for future devices. The coupling enables that the magnetic state can be tuned on demand by an external electric field [1], and by local lattice distortion, strain [2]. A spin-wave, the excitations of the spins, should also be tuned by such external parameters, which is an important property for future magnonics. Here, we conduct resonant inelastic x‐ray scattering (RIXS) at the Fe L-edge to investigate the spin dynamics of BiFeO₃ thin films under various strains. We found that the magnon bandwidth decreases linearly as compressive strain increases. However, our investigation of spin-wave dispersions also captured a strain evolution of the spin-waves, which cannot be explained by a simple scaling of exchange interaction. These findings can bring us a new opportunity for controlling magnons.

[1] Y.-H. Chu et al., Nat. Mater. 7, 478 (2008)

[2] D. Sando et al., Nat. Mater. 12, 641 (2013)