Finite-temperature ferromagnetism of nickel

Abstract

By use of a generalized Hubbard model, we investigate the influence of electron correlations on the temperature dependence of the quasiparticle properties of ferromagnetic Ni. The one-particle energies of the model Hamiltonian are taken from a realistic band-structure calculation. The model contains only two parameters, Hubbard U and the interband exchange J. It is approximately solved by use of a self-consistent moment method. We find a ferromagnetic ground state, mainly caused by the uppermost d subband, a magnetic moment at T=0 of 0.56${\mu }_B$, a Curie temperature of $T_C$=635 K, a Brillouin-type magnetization curve, a strict Curie-Weiss behavior of the paramagnetic susceptibility, a satellite peak some 6 eV below the chemical potential μ as a consequence of strong electron correlations in the uppermost d subband, a temperature-dependent spin polarization of the satellite (≃75% at T=0), temperature-dependent exchange splittings at the top of the d band (0.23–0.36 eV at T=0), and an enhancement factor of the electronic specific heat q(T=0) ≃-0.56. All these results are in excellent agreement with the experiment. For the first time the full temperature dependence of the quasiparticle band structure and the quasiparticle density of states of ferromagnetic Ni are presented.