Effect of cobalt substitution on magnetic properties and microstructure of nanocrystalline (NdDyTb)12.3(FeZrNbCu)81.7B6.0 ribbons

Effect of Co substitution and annealing treatment on the formation, magnetic properties and microstructure of (NdDyTb)12.3(FeZrNbCu)81.7-xCoxB6 (x=0–15) ribbons prepared by rapid quenching and subsequent annealing was systematically investigated by means of differential scanning calorimeter (DSC), X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM) and vibrating sample magnetometer (VSM). Phase analysis revealed single-phase material. The remanence polarization Jr and maximum energy product (BH)max increased with increasing x from 0 to 12 and then decreased for x=15. The intrinsic coercivity Hci of (NdDyTb)12.3 (FeZrNbCu)81.7–xCoxB6 ribbons optimally processed decreased from 1308.7 kA/m for x=0 to 817.4 kA/m for x=15. Optimum magnetic properties with Jr=1.041 T, Hci=944.9 kA/m and (BH)max=155.1 kJ/m3 were achieved by annealing melt-spun ribbon (x=12) at 675 °C for 10 min. There was no significant influence of Co substitution on microstructure.