Magnetic domains and magnetization process of amorphous granular (CoFeB)–SiO2 thin films

The domain structure and magnetization process of a granular film were explored using a Kerr microscope. Narrow line-shaped reversal domains were observed in a granular (Co25Fe66B9)75–(SiO2)25 film, and no increase in the width of the domains was observed during the magnetization reversal process by applying a dc field along the easy axis. In addition, no wall displacement was observed in an ac field along the hard axis because only magnetization rotation occurs due to wall pinning. It was found that wall motion that causes excess eddy current losses at high frequencies is hard to occur by the granular structure