SEM studies of magnetic domains in amorphous ribbons

Static and dynamic observations of magnetic domains in amorphous Fe-B-Si and Fe-B-Si-C ribbons have been made employing a 200 kV scanning electron microscope (SEM) and a special stage allowing in situ application of mechanical stresses and dc and ac magnatic fields. Average domain width in the demagnetized state is found to decrease with increasing demagnetizing frequency, and to be relatively insensitive to tensile stress. Under ac conditions, a great range in the mobility of individual walls is often observed. Some domain walls are strongly pinned, in many cases by obvious surface defects. The implications of these and other observations on hysteresis and eddy-current losses, coercivity, and permeability are discussed.