Origin of the field threshold for in-plane rotation of weak magnetic stripe domains

The in-plane rotation of weak magnetic stripe domains in ~100 nm thick Fe0.8Ga0.2 and Fe:N (Nitrogen implanted) films epitaxied on GaAs(001) was investigated combining magnetic force microscopy, vibration sample magnetometry, and x-ray resonant magnetic scattering measurements. These two systems are characterized by perpendicular energy density K_PMA of the order of 10^5 J/m^3 leading a quality parameter Q = K_PMA/(½ ?_0 M_s^2)< 1 and a consequent weak stripes regime (see Fig. 1). We analysed the behaviour of the stripe pattern under the application of a bias magnetic field along the in-plane direction perpendicular to the stripes, and made a comparison with the analogous behaviour at remanence (Fig.2). The experimental results have been explained by means of energy balance considerations.[1] Fields smaller than 400 Oe for Fe0.8Ga0.2 and 1000 Oe for Fe:N do not induce any stripe rotation. Interestingly, a deformation of the closure domains pattern was evidenced in Fe0.8Ga0.2 leading to a fully reversible magnetization motion. Larger fields produce a sudden rotation of the stripe structure. A phenomenological model is proposed to describe the origin of the critical field. [1] S. Fin et al. Phys. Rev. B 92, 224411 (2015)