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X-ray diffraction and Mossbauer spectroscopy are performed to investigate γ-Fe 1-x Ni x alloys and their nitrides γ'-(Fe 1-x Ni x ) 4 N with corresponding composition. X-ray diffraction shows that both alloys and nitrides have face-centered cubic crystal structure with approximately 18 to 20% expansion in volume of the nitrides. Mossbauer spectra at room temperature show drastic changes before and after nitrogenation. The changes are also rather different for the samples with lower nickel concentrations and those with the higher ones. For x = 0.25 and 0.30, the alloys mainly exhibit paramagnetic singlets while the nitrides exhibit complex ferromagnetic sextets. For x = 0.75 and 0.78, however, the alloys show ferromagnetic sextets while the nitrides show paramagnetic doublets. The reason for this is carefully discussed in terms of the lattice parameter dependence of Curie temperatures, which is caused by the introduction of interstitial nitrogen atoms into the Fe-Ni alloy structure.

Ultrafine (Fe0.7Co0.3)100−xBx amorphous powders with boron content x in the range of 27 to 40 at% are prepared by borohydride reduction without oxide of Fe3+ in the samples. With increasing boron content the average hyperfine field decreases and the average isomer shift increases. Comparing the hyperfine parameters of FeCoB powder with those of FeB powder having the same compositions, it can be seen that the average hyperfine fields and isomer shifts are quite different and the local environment of FeCoB powder is more complicated than that of FeB amorphous powder. DSC results indicated that the stability of the powder increases with increasing B content. Durch Borhydridreduktion werden ultrafeine, amorphe (Fe0.7Co0.3)100−xBx-Pulver mit einem Borgehalt von x im Bereich von 27 bis 40 At% hergestellt. In den Proben befindet sich kein Fe3+-Oxid. Mit wachsendem Borgehalt nimmt das mittlere Hyperfeinfeld ab und die mittlere Isomerverschiebung nimmt zu. Ein Vergleich der Hyperfeinparameter der FeCo;B-Pulver mit denen der FeB-Pulver mit gleicher Zusammensetzung ergibt, das die mittleren Hyperfeinfelder und Isomerverschiebungen vollig unterschiedlich sind und die lokale Umgebung der FeCoB-Pulver komplizierter ist als die der amorphen FeB-Pulver. DSC-Ergebnisse zeigen, das mit wachsendem B-Gehalt die Stabilitat der Pulver zunimmt.