Influence of surface state on the magnetic core loss at high frequency in amorphous Fe-based alloys with low magnetostriction

Magnetic core losses at high frequency up to 100 kHz were investigated on low magnetostrictive amorphous Fe-based alloys annealed in various atmospheres (nitrogen, air and moderate vacuum). The lowest magnetic core loss was attained by the annealing in nitrogen atmosphere. The Auger electron spectroscopy showed oxidation for all the samples annealed at various atmospheres mentioned above, but oxygen concentration for the sample annealed in nitrogen atmosphere sharply drops at about 1000 A depth from the surface, which is quite different from the results of the samples annealed in air and moderate vacuum. The magnetic core loss of the sample annealed in nitrogen atmosphere becomes fairly large from chemical etching, which implies the importance of surface state for the magnetic core loss reduction at high frequency.