Electron spectroscopic evidence of electron correlation in Ni–Pt alloys: comparison with specific heat measurement

We have performed photoemission spectroscopy of Ni–Pt alloys to understand the origin of the discrepancy between the experimental linear coefficient of specific heat γ and that predicted by band theory. We found that the quasiparticle density of states at the Fermi level deduced from photoemission measurement is in agreement with the experimental value of γ, if we include the electron correlation effect. It was also found that the Ni 2p core level satellite intensity increases as Ni content is reduced, indicating a strong electron correlation effect which can enhance the quasiparticle effective mass considerably. This supports our conclusion that electron correlation is the most probable reason of disagreement of γ between experiment and band theory.