Among Fe-based ferromagnets, $\mathrm{La}({\mathrm{Fe}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}{)}_{13}$ compounds are the first example realizing the itinerant-electron metamagnetic transition from the paramagnetic to the ferromagnetic state, accompanied by a marked magnetovolume effects. The effect of pressure on the Curie temperature is one order larger than that on the spontaneous magnetization in analogy with the results for Fe-Pt invar-type alloys. The large pressure coefficient of ${T}_{\mathrm{C}},$ $d\mathrm{ln}{T}_{\mathrm{C}}/dP,$ is attributed to the renormalization effect caused by spin fluctuations for free energy. The metamagnetic transition and the marked magnetovolume effects in the present compounds are related to the characteristic $3d$ band structures in analogy with Fe-Pt alloys in both the ferromagnetic and paramagnetic states.

Large magnetovolume effects and band structure of itinerant-electron metamagnetic La(FexSi1-x)13 compounds

The electronic structure of several ordered phases of the Pt-Fe system is studied using the self-consistent linear muffin-tin-orbital method. The phases studied include nonmagnetic and ferromagnetic ${\mathrm{PtFe}}_{3}$, ferromagnetic ${\mathrm{Pt}}_{2}$${\mathrm{Fe}}_{2}$, antiferromagnetic and ferromagnetic ${\mathrm{Pt}}_{3}$Fe, and ferromagnetic ${\mathrm{Pt}}_{5}$${\mathrm{Fe}}_{3}$. The electronic structure, the densities of states, and the ground-state properties, such as equilibrium lattice constants, bulk moduli, local and average magnetic moments, and the state equations are calculated. The calculated parameters compare favorably with existing experimental data. The cohesive properties, chemical bonding, and the moment-stabilizing mechanism are discussed. A variation of all these aspects with alloy composition illustrates a continuous transition from itinerant to local-moment magnetism. An interplay of the covalent bonding, scalar relativistic effects, electronegativity, and the charge transfer is shown to be responsible for this transition. Homogeneity of the magnetic state of ${\mathrm{PtFe}}_{3}$ Invar is explained. On the basis of the calculated elastic properties and recently reported critical pressures at which the magnetic moment of ${\mathrm{PtFe}}_{3}$ collapses, the total energy difference between the ferromagnetic and nonmagnetic phase is estimated.

Electronic structure of the ordered phases of Pt-Fe alloys.

Electronic densities of states in Y-Co (Y2Co17, YCo5, Y2Co7 and YCo3), Y-Fe (Y2Fe17, Y6Fe23 and YFe3) and Y6Mn23 intermetallic compounds are calculated in the tight-binding d-band model by making use of the recursion method. The average and local magnetic moments on Co and Fe atoms, the high-field susceptibility and the coefficient of the low-temperature specific heat are calculated and compared with the experimental values. The temperature dependences of the spin susceptibility and the spontaneous volume magnetostriction in Y-Fe compounds are also calculated and compared with the experimental results.

http://iopscience.iop.org/article/10.1088/0305-4608/15/7/010/pdf

Electronic structure and magnetic properties of Y-Co, Y-Fe and Y-Mn intermetallic compounds

a b s t r a c t The present work reports on a thermodynamic modeling of the Co-Pt system with ordered fcc phases of L10 and L12 structures by means of the CALPHAD method The liquid, hcp and fcc phases have been modeled as substitutional solutions where the interaction parameters are composition dependent in the form of the Redlich-Kister polynomial The disordered and ordered fcc phases have been modeled in terms of the compound energy formalism with a single Gibbs energy function The obtained phase equilibria and activities of Co and Pt agree well with the available experimental data First-principles calculations are performed to obtain the enthalpies of formation for the ordered fcc phases at 0 K These calculated enthalpies of formations for the ordered phases are less negative than the enthalpies of the disordered state at low temperatures determined from the CALPHAD modeling The Fe-Pt and Ni-Pt systems exhibit the same feature as that in the Co-Pt system, which is discussed in terms of the total magnetic moment of ordered fcc phases

http://www.dl.edi-info.ir/Thermodynamic%20modeling%20of%20fcc%20orderdisorder%20transformations%20in%20the%20Co–Pt%20system.pdf

Thermodynamic modeling of fcc order/disorder transformations in the Co–Pt system

Magnetism in the strained ordered phases of Pt x Fe 1-x and Pt x Co 1-x ( x =0.25, 0.5, and 0.75)

Densities of states of disordered and ordered ferromagnetic Fe3Pt alloys are calculated in the tight-binding d-band model with intra-atomic Coulomb interaction by making use of the coherent potential approximation for disordered alloys and the recursion method for ordered alloys. Magnetic properties such as the magnetisation, local magnetic moments low-temperature specific heat coefficient and spontaneous volume striction are calculated and compared with experiment. It is found that both the ordered and disordered Fe3Pt alloys are strong ferromagnets and that the ground-state properties can be explained by the Hartree-Fock approximation.

https://iopscience.iop.org/article/10.1088/0305-4608/13/12/021/pdf

J Inoue

Papers

A calculation of magnetic properties of Fe3Pt alloys