Magnetostriction of nanocrystalline (Fe,Co)-Si-B-P-Cu alloys

Abstract Amorphous ribbons of composition Fe 85.2-x Co x Si 0.5 B 9.5 P 4 Cu 0.8 (x = 0 at% and 4 at%) have been flash annealed for 10 s at temperatures between 350 °C and 540 °C. Above about 400 °C a nanocrystalline state of bcc Fe(Co) is formed with a crystalline fraction of 50–55% and grain sizes of about 16–18 nm. The optimum nanocrystalline state reveals a saturation polarization up to J s =1.82 T–1.83 T and a coercivity as low as 3–5 A m −1 . The present paper complements the so far missing magnetostriction data for these alloys. Magnetostriction decreases from initially 40 ppm in the as cast amorphous state to about 14 ppm (x = 0 at%) and 19 ppm (x = 4 at%), respectively, after formation of the fully developed nanocrystalline state.