MAGNETOOPTICS APPLIED TO THE ANALYSIS OF MAGNETIZATION PROCESSES IN AMORPHOUS FERRI FERRO MAGNETIC BILAYERS

We study the magnetization processes in the amorphous ferri-ferro magn etic bilayer of GdCo2/YCo2 by means of the transverse magneto-optic Ke rr effect (MOKE). The cycles M cos theta-M sin theta (theta refers to the angle between the magnetization M and the applied field H) indicat e that the irreversible magnetization processes arising at both the co ercivity and the transition field do not occur by a coherent-rotation mechanism. MOKE allows one to follow the creation and the extinction o f Bloch walls in the bilayer as a function of the applied field. First -order magnetization processes are observed in this macroscopic ferrim agnet when H is applied perpendicularly to the in-plane easy axis of u niaxial anisotropy. In fact, sharp transitions in the magnetic-moment structure are observed at H = 8.5 Oe and H = 17 Oe.