A study on the magnetic properties of melt spun Co-Hf-Zr-B nanocomposite ribbons

Abstract

Magnetic properties of melt spun Co86.5Hf11.5-xZrxB2 (x = 0–5) ribbons have been investigated. For the ribbons spun at the wheel speed of 40 m/s, hard magnetic properties with high energy product ((BH)max) of 34.4–52.8 kJ/m3 and intrinsic coercivity (iHc) of 176–216 kA/m were obtained for x = 0–2, but soft magnetic behavior was observed for x = 3–5 due to the appearance of the amorphous phase. By annealing the ribbons with x = 3–5, hard magnetic properties were improved arisen from the formation of magnetically hard phase. The variation of magnetic properties for Co86.5Hf11.5−xZrxB2 ribbons was correlated to microstructure change. Proper Zr substitution for Hf was helpful in refining the grain size from 10–35 nm for x = 0 to 5–15 nm for x = 1, and thus improving the magnetic properties effectively. The optimal hard magnetic properties of Co86.5Hf10.5Zr1B2 ribbons might be originated from the fine magnetically hard Co11(Hf, Zr)2 phase, and the exchange coupling effect among grains and/or with the face-center-cubic Co phase.