High coercivity in non-rare-earth containing alloys

Large coercive fields have been obtained in melt-spun Co-Zr(Hf)-B based alloys. The highest coercivities have been observed in Co76 Zr18 B3 Si3 and Co78 Hf16 B3 Si3 samples with values 6.7 and 6.5 kOe, respectively. The saturation magnetization for both samples is estimated to be around 60 emu/g. Thermomagnetic data showed the presence of two phases with the major phase having a Curie temperature at around 450 °C. TEM and SEM studies showed a microstructure consisting of a mixture of two phases with the grain size in the range of 1000–5000 Å. The origin of the high coercivity is believed to be due to the fine grain microstructure leading to a single-domain particle-type behavior.