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: Tight Binding Linear Muffin-Tin Orbital (TB-LMTO) electronic calculations are presented for the magnetic and structural properties of ordered and disordered FeAl alloys. The total energy, bulk modulus, lattice parameter and magnetic moments of B2, D03 and B32 ordered structures and A2 disordered structure were calculated for different compositions. The different structures are obtained by varying the position of Fe and Al atoms in a BCC superstructure. In this way, we examine the order-disorder transition that takes place in these alloys. Disordered alloys present both larger Fe magnetic moment and lattice parameter than ordered ones. In this work comparison of the calculated quantities with available experimental results is provided and it can be concluded that the results are in quantitative agreement with the experimental trends. [ABSTRACT FROM AUTHOR]

Disordered Fe70Al30 alloy was measured versus annealing temperature by X-ray diffraction, differential thermal calorimeter, magnetization and Mo¨ssbauer 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. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

Abstract: The magnetic behaviour of Fe-based magnetic systems has been studied theoretically and experimentally for many years [E.P. Wohlfath, K.H.J. Buschow, Handbook of Ferromagnetic Materials, vol. 4, North-Holland Elsevier Science Publishers, Amsterdam, New York, Oxford, Tokyo, 1988 (Chapter 1)]. Starting with Al dissolved in Fe, the first stable structure is the D03 cubic structure and it exists over the range 23–37at% Al. In this range these alloys present interesting magnetic properties. The other stable compound existing over a wide range of composition is FeAl which is also cubic, with the B2 structure (CsCl), and it exists over the range 37–50at% Al. On the other hand, the FeAlSi alloys show the D03 structure, but do not show the B2 structure. The effect of Si in these alloys is double; on the one hand, it contributes to the decrease of the lattice parameter which, as reported by Nogues et al. [Phys. Rev. B 74 (2006) 024407], has a major influence on the magnetism and, on the other hand, having one more p electron than the Al atom, it promotes the charge transfer from Si to Fe atoms, as reported by Legarra et al. [Hyperfine Interact. 169 (2006) 1217–1222]. In this work, we perform ab-initio electronic calculations by means of tight binding linear muffin-tin orbital (TBLMTO) and Vienna Ab-initio Simulation Package (VASP) in order to study the magnetic contribution of Si/Al substitution in the FeAl alloys. [Copyright &y& Elsevier]

Abstract: In FeSiAl alloys, when Si substitutes for Al, important changes take place in the magnetism as well as in the structural properties. Alloys in the two composition series Fe75Al25− x Si x (x=0, 7.5, 12.5, 17.5, 25) and Fe70Al30− x Si x (x=0, 9, 15, 21, 30) were prepared by induction melting; afterwards they were crushed and then annealed in order to recover the DO3 stable phase. The deformed FeAl samples show larger lattice parameters than the ordered ones; however, this difference (Δa) decreases when Si substitutes for Al until it becomes zero (i.e. until the ordered samples and the deformed ones have the same lattice parameters). This trend is the same for both sample series and does not depend on the Fe content of the alloy. However, the magnetization has a different behaviour depending on the Fe content. For deformed Fe75Al25− x Si x alloys the saturation magnetization decreases with increasing Si content while for Fe70Al30− x Si x deformed alloys the saturation magnetization has a plateau in which the saturation magnetization values do not vary. [Copyright &y& Elsevier]