Effect of niobium addition on magnetization reversal behavior for SmCo-based magnets with TbCu7-type structure

The effect of Nb addition on the microstructure and magnetic properties of nanocrystalline Sm(CobalNbxZr0.02)7 permanent magnet were investigated. The magnetization reversal behavior for ball milled Sm(CobalNbxZr0.02)7 samples with high coercivity was investigated by analyzing hysteresis curves and recoil loops of demagnetization curves. Nb addition proved to result in relevant improvement in the magnetic properties, especially in the coercivity Hc. It was shown that the magnetic properties of Sm(CobalNbx- Zr0.02)7 nanocrystalline magnets were improved by an additional 0.06 at.% Nb. In particular, Hc was improved from 602 to 786 kA/m at room temperature. The maximum value of the integrated recoil loops area for 0.06 at.% Nb-doped samples of 1.81 kJ/m3 was much lower than that of the Nb-free sample, which could be explained by a smaller recoverable portion of the magnetization remaining in the Nb-doped sample when the applied field was below the coercivity Hc. The nucleation field Hn for irreversible magnetization reversal of the magnetically hard phase were calculated by analyzed in terms of the ΔMirrev-H curve and the Kondorsky model.

Graphical AbstractDependence of –Mirrev (H)/2Mr (∞) as a function of the applied reversal field for Nb-free and 0.06 at.% Nb-doped Sm(CobalNbxZr0.02)7 alloys (The nucleation field data Hn (608 kA/m for the Nb-free and 780 kA/m for the Nb-doped samples, respectively) are shown in the plot)Figure optionsDownload as PowerPoint slide