Angle-resolved photoemission spectra, electronic structure, and spin-dependent scattering in ${\mathrm{Ni}}_{1-x}{\mathrm{Fe}}_x$ Permalloys

We present the all-electron charge and spin self-consistent electronic structure of ${\mathrm{Ni}}_{1-x}{\mathrm{Fe}}_x$ Permalloys for a range of Fe concentrations, using the first-principles Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) scheme to treat disorder and the local spin density approximation to incorporate exchange-correlation effects. Recent high-resolution angle-resolved photoemission spectroscopy (ARPES) experiments on ${\mathrm{Ni}}_{0.90}{\mathrm{Fe}}_{0.10}$ and ${\mathrm{Ni}}_{0.80}{\mathrm{Fe}}_{0.20}$ Permalloys are analyzed in terms of the spectral density function, $A_B({\mathbf{k}}_{\Vert },{\mathbf{k}}_{\perp }=0{,E}_F),$ computed from the KKR-CPA Green function for ${\mathbf{k}}_{\Vert }$ values varying along the $\Gamma -K$ direction in the Brillouin zone. The widths of the majority as well as the minority spin peaks in the theoretical spectra are in excellent accord with the corresponding ARPES results in all cases, suggesting that spin-dependent disorder scattering constitutes the main scattering mechanism for the carriers in the Permalloys. Majority spin states of Ni are virtually undamped by the Fe impurities, while the minority spins at the Fermi energy ${(E}_F)$ are heavily damped. The nature of the Ni and Fe potentials in the Permalloys is explored in detail. The effective disorder parameter in the alloy is found to be strongly dependent on the energy, momentum, spin, and symmetry of the specific states involved. The evolution of the electronic states on the Ni and Fe sites as a function of Fe concentration is discussed. The magnetic moments on Ni as well as on Fe are found to remain essentially unchanged with increasing Fe content.