Strain‐Gradient‐Induced Unidirectional Magnetic Anisotropy in Nanocrystalline Thin Permalloy Films

Herein, the effect of inhomogeneous elastic deformation on the magnetic anisotropy of Ni 71.5 Fe 28.5 wt% nanocrystalline films is investigated. The in‐plane controlled strains are induced in the film by bending of a glass substrate which has a thickness step in the middle. Ferromagnetic resonance measurements reveal the existence of in‐plane unidirectional magnetic anisotropy. The anisotropy behavior directly correlates with the calculated strain gradients. It is shown that this correlation is well explained by the flexomagnetic effect, which establishes the relation between the magnetization and the inhomogeneous strains. The experimental value of the flexomagnetic coefficient for the thin Ni 71.5 Fe 28.5 wt% film is 1.5 × 10 −3 T m.