Magnetic aftereffect due to domain wall motion in amorphous Tb-Fe sputtered films

A very large aftereffect is observed in sputtered amorphous Tb-Fe films with uniaxial anisotropy perpendicular to the film plane. In the present experiment, the film is first saturated to -M_s by a premagnetizing field H_p (<0), where M_s is the saturation magnetization. Then the applied field is suddenly changed from H_p (<0) to H_a (?0) which is close to the coercive field. With proper choice of the film composition, temperature, H_a and so on, the magnetization changes from -M_s to almost +M_s with the passage of time while H_a is kept constant. The dependences of the aftereffect on the applied field and on the temperature are shown. The domain observation by means of polar Kerr effect reveals that the aftereffect is associated with the slow dendritic growth of the magnetic domains. It is also found that the density of reversed domain nuclei depends on the premagnetizing field H_p.