Presence of enhanced Pauli spin response and 6 eV plasmonic excitation in Ni metal

We revisit the electronic structure of Nickel (Ni) using the density functional theory (DFT) and dynamical mean-field theory (DMFT) for the theoretical description of its electronic structure properties along with finite-temperature magnetism. Our study provides a comprehensive account of electronic and magnetic properties with the same set of Coulomb interaction parameters,<i>U</i>= 5.78 eV and<i>J</i>= 1.1 eV calculated using first-principles approach. The nature of theoretical magnetization curves obtained from DFT and DFT + DMFT as well as the experimental curve show deviation from the standard models of magnetism,<i>viz</i>Stoner and spin fluctuation model. In comparison to DFT+DMFT method, temperature dependent DFT approach is found to well describe the finite-temperature magnentization curve of Ni below critical temperature (T⩽ 631 K). The study finds significant Pauli-spin susceptibility contribution to paramagnetic spin susceptibility. Excluding the Pauli-spin response yields a linear Curie-Weiss dependence of the inverse paramagnetic susceptibility at higher temperatures. Also, the presence of mixed valence electronic configuration (3<i>d</i>⁸, 3<i>d</i>⁹and 3<i>d</i>⁷) is noted. The competing degrees of both the itinerant and localized moment picture of 3<i>d</i>states are found to dictate the finite-temperature magnetization of the system. Furthermore, the quasiparticle scattering rate is found to exhibit strong deviation from<i>T</i>²behavior in temperature leading to the breakdown of conventional Fermi-liquid theory. In addition to the 6 eV satellite, our calculated electronic excitation spectrum shows the possible presence of satellite feature extending ∼10 eV binding energy, which has previously been reported experimentally. Interestingly, ourG0W0results find the presence of plasmonic excitation contribution to the intensity of famous 6 eV satellite along with the electronic correlation effects, paving way for its reinterpretation.