Effects of surface oxidation on magnetic properties of amorphous alloy forchoke core use

In order to develop a non-gap type choke core, effects of annealing in oxyg en atmosphere on magnetic properties for FeCrBSiC amorphous alloy were inve stigated. After annealing for 2 hrs at 480 degrees C, optimum magnetic prop erties for choke core were obtained, where the effective permeability was a bout 400 and was almost constant up to 1 MHz, and the decrease in permeabil ity upon large bias de current of 16 A was very little. Furthermore It was shown that the ac magnetic loss was very low as compared to the conventiona l choke cores. With the increase In annealing temperature the magnetic hyst eresis loop was inclined without a substantial increase of coercive force a nd a microstructural change of amorphous phase up to 480 degrees C. It was considered that these choke properties were basically due to the interactio n between oxidation-induced stress and magnetostriction which brought about the induced magnetic anisotropy perpendicular to the ribbon surface, and a lso the good soft magnetic properties of amorphous phase.