The magnetic properties of sigma phase alloys

On the magnetism of the σ‐phase Fe–Cr alloys

“…The reason for the difference in the latter follows from the fact that although at comparable temperature and field values the magnetization for samples with the same composition is in complete agreement with the one reported in [4], at B a = 15 T, however, the present values are much higher. The linear dependence on B a proposed in [4] to start already at 1 T is obtained in this study only for B a ≥ 6 T. Consequently, our 〈µ〉-values are systematically higher. The upper limit for the critical concentration of the existence of the sigma-phase as estimated from the 〈µ〉 (x)-dependence is equal to 53.6 at% Cr.…”

“…Sumimoto et al also fitted their spectra in terms of three subspectra but without quadrupole splitting [3]. Following X-ray [4,8] and neutron diffraction [9] experiments as well as recent theoretical calculations [10] Fe atoms do occupy all five possible sites. A question, however, arises whether or not the four-or three-site model is justified as far as the analysis of Mössbauer spectra is concerned.…”

“…The authors of that paper also noted that the non-saturating behaviour of the isothermal magnetization curves can be taken as additional evidence in support of that model. However, those curves were recorded in an external magnetic field B a ≤ 2 T, which could have been not large enough to saturate the moments [4]. To shed more light on the magnetic properties of the sigma-phase Fe-Cr alloys, and, in particular, on its nature, systematic magnetization and 57 Fe Mössbauer-effect measurements were performed both as a function of temperature and external magnetic field of up to 15 T. The results obtained are presented and discussed in terms of the two models mentioned above.…”

Magnetic ordering above room temperature in the sigma-phase of Fe66V34

“…First, we found that the values of <µ> determined from magnetization measured in external magnetic fields, B a , up to 15 T were shifted by ~0.1 µ B to higher values in comparison with their counterparts derived from similar curves recorded in an external field of 1 T [6,7]. This difference follows from the ill-defined extrapolation condition of the magnetization measured in the external magnetic field of 1 T to B a = 0 T.…”

Sigma-Phase in Fe-Cr and Fe-V Alloy Systems and its Physical Properties

“…σ -FeCr and σ -FeV are known to have well evidenced magnetic properties. [2][3][4][5][6][7][8] From the two, the σ -FeCr is regarded as the archetype, because it was the Fe-Cr system in which the presence of the σ phase was suggested as early as 1907 for the first time to occur. 9 However, its real discovery came only 20 years later when Bain and Griffits 10 (and independently Chevenard 11 ) found in a Fe-Cr-Ni alloy a hard, very brittle and non-magnetic phase which they termed as the "B constituent."…”