Rotatable magnetic anisotropy in a Fe0.8Ga0.2 thin film with stripe domains: Dynamics versus statics

A comprehensive investigation of rotatable anisotropy in a Fe0.8Ga0.2 thin film with a stripe domain structure has been performed comparing static and dynamic measurements. The stripes’ domain formation and their rotation under a transverse magnetic field have been imaged by magnetic force microscopy. The rotatable anisotropy field Hrot was determined by fitting the frequency evolution of the dipole-dominated magnetostatic spin-wave mode versus the in-plane orientation of the stripe domains, measured by Brillouin light scattering in the absence of any dc or ac magnetic field. We obtained Hrot ≈ 1.35 kOe, which is nearly ten times larger than the crystallographic in-plane anisotropy field. By applying a dc magnetic field along the stripes’ axis, Hrot decreases, and eventually vanishes for saturated in-plane magnetization. At remanence, we established a quantitative relationship between static and dynamic properties, that is, the stripes’ rotation angle and the in-plane angle dependence of spin-wave frequency.