On the magnetic excitations in nickel

TLDR: By comparing measured and calculated versions of the generalized magnetic response function of nickel over a wide range of temperatures, it is shown that the much-discussed simple model of an itinerant-electron ferromagnet based on a random-phase approximation treatment of the Hubbard Hamiltonian accounts, in its essentials, for the magnetism of that substance as mentioned in this paper.

Abstract: By comparing measured and calculated versions of the generalized magnetic response function of nickel over a wide range of temperatures it is shown that the much-discussed simple model of an itinerant-electron ferromagnet based on a random-phase-approximation treatment of the Hubbard Hamiltonian accounts, in its essentials, for the magnetism of that substance. Thermal neutron inelastic scattering techniques were used to explore the whole Brillouin zone of wave vectors K in nickel up to energies ▄ω of some 2k B T C over the range of temperatures up to 2T C; the computations were based on direct evaluation of the Lindhard expression for the generalized susceptibility, using a tight-binding band structure, followed by exchange enhancement of the spin part as per Izuyama, Kim and Kubo. The contribution to the neutron scattering from orbital motion of the electrons was estimated to be small, and in a special experimental investigation a satisfactorily low upper limit on this quantity for our present p...