Influence of Co content on the structure and magnetic permeability of nanocrystalline (Fe1−xCox)73.5Cu1Nb3Si13.5B9 alloys

Structural and soft magnetic response of nanocrystalline (Fe1−xCox)73.5Cu1Nb3Si13.5B9 (x = 0, 0.25, 0.5, 0.75) alloys were investigated. Influences of heat treatment and Co content on the crystallization were analyzed through estimation of the crystalline volume fraction Vcr and thickness of the intergranular amorphous layer Λ from XRD patterns. High-temperature soft magnetic response was analyzed by the temperature evolution of the magnetic permeability from room temperature to 780 °C. It was found that the high-temperature soft magnetic behavior is improved with increasing Co content for x ≤ 0.5, which is ascribed to reinforcing magnetic coupling between the crystals, however, a decrease of μi was observed for the Co richest sample. The observed μi behavior as a function of Co content is interpreted in terms of variations in the degree of exchange coupling.