Fe-57 Mossbauer study of perovskite-type Fe-Ni nitrides gamma '-(Fe1-xNix)(4)N (0 <= x <= 0.8)

Perovskite-type Fe-Ni nitrides gamma'-(Fe1-xNix)(4)N in the 0 less than or equal to x less than or equal to 0.8 range have been investigated by Mossba uer spectroscopy. Mossbauer spectra have been recorded at low temperatures (4.2 or 20 K), at similar to 300 K and above the Curie temperature of each sample. The quadrupole splitting at the Fe II (cube face center) site was l arge and increased upon Ni substitution, exceeding 1 mm/s. The low-temperat ure Mossbauer spectra were fitted with magnetic and quadrupole hyperfine in teractions combined with a binomial distribution of Ni nearest neighbors. T he fitting results indicated that the direction of the easy magnetic axis u ndergoes a transformation from [0 0 1] to [1 1 1] for increasing Ni substit ution. The hyperfine field at Fe I (cube corner) site increased anomalously with x, while it remained nearly constant at Fe II site. The isomer shift did not exhibit any significant change in the whole range of Ni concentrati on at both Fe I and Fe II sites. (C) 2000 Elsevier Science B.V. All rights reserved.