On the effect of Al addition on the phase composition and magnetic properties of NdFeB permanent magnet alloys

Abstract

The phase constitution of the Nd16(Fe1–xAlx)76B8 permanent magnets alloys for 0.0≦x≦0.20 is studied by means of thermomagnetic analysis and Mössbauer spectroscopy. A second magnetic phase with a Curie temperature of 170 °C coexists with Al doped hard magnetic boride for 0.10≦ ≦x≦0.15; this phase is reabsorbed after long thermal treatments; nevertheless, this is the only magnetic phase for x = 0.20. The presence of tetragonal paramagnetic boride NdFe4B4 is detected in the whole range. The Mössbauer spectra for 0.10 ≦x≦0.20 are reported and discussed. Both, the anisotropy field and intrinsic saturation magnetization decrease with the Al content.