Nanocrystalline exchange-coupled Pr-Fe-B permanent magnets

Nanocomposite Pr₂Fe₁₄B/α-Fe permanent magnets were prepared by melt spinning and subsequent crystallizahon of Pr₈Fe₈₆B₆, amorphous Precursnors. The microstructure is a two-phase nanocomposite of Pr₂Fe₁₄B and soft magnetic α-Fe with an average size of 30nm. X-ray diffration, Thermomagnetic analysis and TEM analysis indicate that amorphous Pr₈Fe₈₆B₆, alloy crystallizes through the process of Am→Am'+α-Fe→Pr₂Fe₂₃B₃+α-Fe-Pr₂Fe₁₄B+α-Fe. The highest value of remanence (B_r), cocreivity (H_ci) and maximum energy Product ((BH)_max) of the nanocrystalline alloys are 1.10T, 340 kA/m and 110 kJ/m³ respechvely, exhibihng remarkable remanence enhancement. The effect of annaling temperature and time on the microstructure and magnetic properties was also studied. The results show that appropriate annealing temperature and time are important for obtaining the optimal microstructure and the bestmagnetic properties.