Theoretical study of the intrinsic magnetic properties of disordered Fe1−xRuxFe_{1-x}Ru_x alloys: a mean-field approach

The magnetic properties of the $Fe_{1-x}Ru_x$ alloy system for 0 $\leq$ x $\leq$ 0.10 are studied by using a mean-field approximation based on the Bogoliubov inequality. Ferromagnetic Fe-Fe spin correlations and antiferromagnetic Fe-Ru and Ru-Ru exchanges have been considered to describe the temperature dependence of the Curie temperature and low temperature magnetization. A composition dependence has been imposed in the exchange couplings, as indicated by experiments. From a least-square fitting procedure to the experimental results an estimation of the interaction parameters was obtained, which yielded the low temperature dependence of the magnetization and of the ferromagnetic Curie temperature. A good agreement was obtained with available experimental results.Comment: Two figures, to appear in J. Phys. Cond. Matte

Electronic structure of A15-type compounds: V 3Co, V 3Rh,V 3Ir and V 3Os

71.15.Ap Basis sets, 71.20.Lp Intermetallic compounds, 74.25.Jb Electronic structure, 74.70.Ad Metals; alloys and binary compounds,

Electronic structure and magnetization of Fe–Co alloys and multilayers

The magnetic properties and electronic structure of bcc Fe–Co alloys and multilayers are investigated with the first-principles molecular cluster discrete variational method. The density of states and the contact interactions are obtained for the central atom of each cluster. Besides the local magnetic moment and the isomer shift the occupancies of 3d, 4s, and 4p shells are investigated when Co atoms are introduced in the immediate vicinity of iron sites. The calculations indicate a varying magnetic moment for Fe atoms and a constant value for Co atoms which is in agreement with experiments. For the superstructures, our results indicate a strong dependence of the local moment, contact field, and isomer shift for Fe atoms with the thick of iron layers. The internal field increases for thicker Fe layers while the local moment decreases which is also in accordance with experimental predictions

Martensitic phase transition from cubic to tetragonal V

In this study we focus on the subtle changes which occur in the electronic structure and in the Fermi surface topology with the low temperature (21.3 K) cubic → tetragonal martensitic phase transition in V3Si. From the calculations it has been verified the occurrence of a charge transfer from V atoms to Si atoms, with the phase transition to a tetragonal variant of the A-15 structure. The orbital population of s- and p-states of V atoms in the 2e and 4k sites of the tetragonal phase are practically the same. Major differences are seen in the occupation of d-states. There is a decrease in the average electronic energy with the structural transition, which occurs as a result of the emptying of V d-states (mostly from bands 19–20), and these electrons enter preferentially into the Si p-orbitals. The present results thus indicate that the electronic features of the martensitic transition of V3Si, besides being intimately related to the splitting of the Γ12 into the Γ1+ and Γ3+ states and the position of the Γ1+ state relatively to EF, is mainly associated with the gain in the average electronic energy which occurs from an electron transfer from V-d → Si-p states. This is the main source to explain the stability of the tetragonal phase formed at low temperature in this system

Density functional theory study of Fe(3)Ga

First-principles scalar relativistic calculations in supercells of 16 atoms are used to represent disordered B2 ordering of Fe(3)Ga in order to observe the effect of Ga-Ga pairs on the electronic structure of this alloy. From a comparison with pure bcc Fe it is observed that the energy position and occupation of e(g) and t(2g) states are largely affected by the Ga-Ga pairs and strengthened intraplane interactions takes place. The results show that a larger hybridization of the conduction band is in the source of the magnetostriction enhancement experimentally observed in Galfenol. (C) 2011 American Institute of Physics. [doi:10.1063/1.3525609