57Fe Mossbauer investigation of R2(Fe1-xCox)17Ny (R=rare earth, x less than or equal to 0.4, y less than or equal to 2.2)

The effects of different contents of nitrogen in both Pr2Fe17 and Nd2Fe17 and of cobalt in both Nd2Fe17 and Nd2Fe17N2 center dot 2 are investigated by means of Mossbauer spectroscopy (MS) and thermal magnetic analysis (TMA). The results confirm that either nitrogen or cobalt increases the hyperfine field (Bhf) as well as the Curie temperature (Tc) of the material. The hyperfine parameters for nominal contents of nitrogen above y = 1.5 are the same as those observed in fully nitrided samples. Our data also reveal that the combination of both N and Co produces an additional increase of Tc. The same behaviour is observed in Bhf of Nd2(Fe1-xCox)17N2 center dot 2 in the range 0 < x < 0.1. After a restricted maximum at x approximately equal to 0.02-0.05, Bhf decreases with increasing x.