Figure 1 : Curie temperatures and self-energies of iron and nickel.

From: Local magnetic moments in iron and nickel at ambient and Earth’s core conditions

Figure 1

Ferromagnetic order parameter in bcc iron (a) and in fcc nickel (b) as a function of temperature, whereas N (N) are the total number of spin-up (-down) electrons in the correlated d orbitals. The Curie temperature TC is signalled by the magnetization dropping to zero. For nickel, we obtain TC=600 K, very close to the experimental value of 633 K (ref. 16), indicated by the black arrow in b. Our estimated TC for iron is around 1,500 K, that is, roughly 30% larger than the experimental one of 1,043 K (ref. 16), marked by the black arrow in a (for a discussion, see ‘Methods’ section, where also a description of the three parametrization used for the Coulomb interaction is given). Imaginary part of the Matsubara self-energies of iron (c) and nickel (d) at β=30 eV−1 in the paramagnetic phase. The curves with filled circles show one of the degenerate t2g orbitals, with empty circles one of the degenerate eg orbitals. The lifetime of the quasiparticles is inversely proportional to . Contrary to nickel, the scattering rate in iron at ambient pressure is large, even though the insulating-like shape of the density–density eg-self-energy is replaced by an upturn at small frequencies in Kanamori and full Coulomb.