Band Structure and Fermi Surface of Ferromagnetic Nickel

The band structure and Fermi surface of ferromagnetic Ni were studied using Mueller's combined interpolation scheme, extended to include spin-orbit and exchange interactions. Uniform exchange splittings were included in the molecular-field approximation. Semiempirical band structure were obtained which gave detailed agreement with experimental data where they were available, and over-all agreement with the results of ab initio calculations. In particular, good fits were obtained to the $X$ pocket and $L$-neck de Haasvan Alphen data, magnetic breakdown effects, optical edges, and valence (i.e., 10.00 electrons/atom). It was possible to fit the $X$ pocket Fermi surface using a "partial" two-center approximation to the tight-binding $d$ parameters. The $X_5$ quasiellipsoidal pocket was found to have an unusual shape, resulting from anisotropic interaction with the neighboring $X_2$ band. Moreover, the $d$ bands were sufficiently high in energy that the $X$ pocket had some $s-p$ character along its major axis. Many-body mass enhancement factors were found to be nearly uniform (≈ 2) after the light-mass $s-p$ character was added to the $X$ pocket. For the $d$-band exchange splittings, values of 0.4-0.6 eV were found, depending on assignments of optical edges. The density of states showed a sharp multipeaked structure, which, when smeared out, gave qualitative agreement with the density of states obtained from recent ultraviolet photoemission studies.