Moessbauer and thermomagnetic analysis of Al-containing Nd-Fe-B permanent magnet alloys

Arc melted polycrystalline samples with nominal composition Nd16(Fe1-xAlx)76B8(0.0 ≤ x ≤ 0.15) are analyzed by means of thermomagnetic analysis and Moessbauer spectroscopy. In the as-cast state only one ferromagnetic phase crystallizes for x ≤ 0.08, and is identified as the doped Nd2Fe14B alloy. For a higher Al content, a second magnetic phase is detected with a Curie temperature of about 170 0C. In the composition range studied, the Curie temperature of the Al substituted tetragonal magnetic phase decreases linearly with the x increase. Moessbauer spectra revealed the presence of a paramagnetic phase identified as the NdFe4B4 compound and suggest a non-preferential occupancy of Al atoms over the different cation sites. (author)