A high permeability Fe-Ni base glassy alloy containing Mo

This paper reports some of the low field magnetic properties, and their stability, obtained for a glassy Fe40Ni38Mo4B18 (METGLAS- Alloy 2826MB) alloy, which has a Curie temperature of 626 K, room temperature saturation induction of 8.8 kG and a linear magnetostriction of about 9 ppm. When optimally field-annealed, the toroidally wound material shows a coercivity of about 7 mOe, remanence of 7.5 kG and a dc permeability (at B=100 G) of about 45 000. The material’s ac core loss at B=1 kG and f=104 Hz is close to that (∼1.3 watts/kg) of a tape-wound crystalline 4-79 Mo Permalloy core of similar size. The high frequency effective permeability is ∼700 at f=5×105 Hz. This is a factor of ∼7 greater than for 4-79 Permalloy. The thermal stability of these properties is found to be excellent. The improved thermal and magnetic properties of the present material over Fe-Ni-P-B glassy alloys significantly enhance the opportunity to apply these materials in various magnetic applications.