Magnetic properties improvement of melt spun Co86.5Hf11.5B2 nanocomposites by refractory elements substitution

Last decades, rare-earth (RE) containing nanocomposites with improved remanence, B_r, and maximum energy product, (BH)_max, have been investigated extensively for bonded magnet applications. However, the demand for rare-earth permanent magnets is rapidly increased, leading to the shortage and price rising of rare earth elements. Therefore, it is significant to explore the RE-free permanent magnetic materials which are possible for industrial applications. Recently, RE-free Co-Hf-B system has been reported to exhibit attractive permanent magnetic properties. Especially, Br=0.75T, _iH_c = 248 kA/m, and (BH)_max = 61.6 kJ/m³ have been achieved in Co₈₅Hf₁₂B₃ recently. However, limited study related to the elemental substitution effect on the magnetic and structural characterizations of Co-Hf-B alloys is available. In the paper, Co-rich Co_86.5Hf_11.5B₂ is selected as an initial composition, and the effect of refractory elements substitution, including Ti, Cr, Nb, Zr, on the structural and magnetic properties of Co_86.5Hf_10.5MB₂ alloys are investigated. The melt spinning method is adopted to prepare the isotropic nanocomposite samples at a high wheel speed of 40 m/s in this work.