[en] Theoretical calculations in ordered and disordered FeAl alloys, performed by the TB-LMTO code, indicate that the contribution to the reinforcement of the magnetism in the order-disorder transition of these alloys depends on their Fe content. Close to the equiatomic composition the intrinsic disorder contribution is the largest one. However, for lower Fe contents the volume change contribution increases and for Fe₃Al both contributions are similar

[en] The degree of order in Fe-Al intermetallics has an important influence on their magnetic properties. Moreover, the disorder-order transition provokes a dramatical change on the magnetism of these alloys. In order to clarify this phenomenon, neutron diffraction and Moessbauer spectroscopy measurements have been made. The results show that the reordering process occurs in two stages, the first of which occurs at about 150 deg. C while the second takes place at around 350 deg. C. The change of magnetic properties is observed to be related to the decrease of A2 phase content and decreasing lattice parameter

[en] The whole crystallisation process of three Fe-rich FeZr metallic glasses has been studied using in situ neutron thermo-diffraction. While the beginning of the transformation occurs at the same temperature, the further evolution is strongly compositional dependent. Metastable BCC-Fe phase appears at intermediate temperatures only in Fe₇₅Zr₂₅ alloy. From this study a clear evidence of the existence of an FCC-Fe_3+xZr is shown

No abstract available

[en] Disordered Fe₇₀Al₃₀ alloy was measured versus annealing temperature by X-ray diffraction, differential thermal calorimeter, magnetization and Moessbauer spectroscopy. All of them show a critical behaviour around 475 K. The critical behaviour is related to an ordering of the alloy that happens at that temperature linked to a decrease of the magnetic properties of the sample

[en] Positron lifetime measurements are used to study the recovery of vacancies in pure and H-doped Nb and Ta after low-temperature irradiations. After 3 MeV electron irradiation the lifetime in pure Nb and Ta increase to tau/sub v/ = 205 psec due to positron trapping at monovacancies. During annealing of the specimens the vacancy migration is observed at 230 K in Nb and at 280 K in Ta. In H-doped specimens the trapped positron lifetime at vacancies is smaller (170 psec in Nb and 180 psec in Ta), which indicates that vacancies are decorated by hydrogen atoms. Hydrogen shifts the vacancy migration up to 380 K in Nb and 450 K in Ta

[en] Thermal dependence of both magnetic and structural properties of crystalline ribbons with the nominal composition Fe₆₆Cr₁₂Al₂₂ were investigated by X-ray diffraction, ⁵⁷Fe Moessbauer spectrometry and magnetic measurements. An improvement of the magnetic properties of the ribbon has been observed, which can be due to both structural relaxation and defect effects, which are created during the thermal treatment

[en] Amorphous alloys of composition Fe₈₆Zr₇Cu₁B₆ have been prepared and annealed in the temperature range from 570 to 950 K, obtaining several degrees of nanocrystallization. Magnetic and Moessbauer measurements show the different phases that appear in the samples after the heating, and their percentage, depending on the annealing temperature. The Curie temperature of the amorphous phase is shown to remain almost unchanged during the crystallization. Moessbauer spectroscopy however, reveals subtle changes in the structure

[en] As-cast ferromagnetic amorphous alloys of nominal composition (FeTM)₈₀B₂₀ have been studied by Moessbauer Spectroscopy, being TM one transition metal atom, Ni, Cr, Mo or Pd. A detailed analysis of the isomer shift, IS, and hyperfine field distribution, HFD, at Fe sites is reported in order to achieve some conclusions about the Chemical Short Range Order and the electronic structure in these alloys. HFD changes found in (FeNi)B for Ni rich concentrations suggest the existence of Fe atoms strongly interacting with Ni. Small amounts of Cr and Mo shift the HFD to lower values of hyperfine field, B_hf, while Pd enhances the B_hf

[en] The classification of the elements has been one of the major achievements of Science. Since then the resulting periodic order has been most strikingly reflected in a quantitative manner by most of the physical properties of the elements. The aim of this paper is to show the strong relation between the atomic volume and the positron lifetime of the elements of the periodic table. The differences between the BN, LDA and GGA schemes of calculations are pointed out too. (orig.)