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The effects of the cooling rate on the microstructure and magnetic properties of the melt-spun Nd60Fe30Al10 alloys are investigated by Mossbauer Effect (ME) spectroscopy and magnetic hysteresis loops measurements at different temperatures. It is found that the hard magnetic properties of these alloys are likely to be related to the presence of clusters of a metastable crystalline μ-type phase. It is observed that as the cooling rate increases, the amount of this magnetic μ-like phase component decreases in the benefit of an amorphous Nd-rich phase. This phase has an iron concentration, which increases with increasing the wheel speed, is paramagnetic at room temperature and becomes superparamagnetic below approximately 50 K and 100 K for slow and high cooling rates, respectively.

The structural changes produced during the mechanical grinding of the crystalline compounds ZrFe 2 and HfFe 2 (Laves phases) were analyzed by means of Mossbauer effect spectroscopy on 57 Fe , perturbed angular correlations of gamma rays on 181 Hf and X-ray diffraction. For the starting crystalline compounds the hyperfine interaction at both sites (T and Fe) is mainly magnetic with a weak electric quadrupole perturbation. The Mosssbauer spectra in both systems rapidly evolves with grinding time showing an increasing fraction of nuclei experiencing a pure quadrupole interaction. On the other hand, the nuclear spin precession curve changes monotonically and the fitted hyperfine parameters show that while the quadrupole perturbation increases the magnetic one remains nearly unchanged at Hf sites. The results show that after a severe grain size reduction partial amorphization and Fe segregation occurs probably as a consecuence of the surface energy accumulation and/or ambient contamination.

Preliminary results on order-disorder transformations in mechano-synthesized Fe 75 Ge 25 and Fe 60 Al 40 , as well as on tools contamination of elemental samples, are presented. In the first case the system forms in the disordered cI2-W structure, but orders into the cF16-BiF 3 structure when treated a T ≤ 673 K, or into the hP8-Ni 3 Sn one when annealed at 1073 K. Mechanical work induces the hP8-Ni 3 Sn structure to transform back into the cI2-W one. Disordering by mechanical work of cP2-CsCl-type Fe 60 Al 40 , gives raise to the apparition of magnetic hyperfine interactions in the RT Mossbauer spectra. Tool contamination of elemental samples treated in a planetary mill with chrome steel vials and balls could be tentatively described in terms of their Poisson ratio, rather than in terms of either their Young, shear or bulk moduli, or of the Fe-element enthalpy of mixing.