Experimental and Calculated Photoelectron Energy-Distribution Curves of Ni above and below the Curie Temperature

Abstract

Theoretical photoelectron energy-distribution curves (EDC) of Ni were calculated using an interpolated band structure with an exchange splitting of the ferromagnetic bands of 0.37 eV at $E_F$. From paramagnetic to ferromagnetic Ni, the leading peak of the EDC originating from $d$ bands near $E_F$ is predicted to shift 0.25 eV over the range $7.7<~\hslash \omega <~10.7$ eV (assuming direct transitions) and 0.18 eV (assuming nondirect transitions). High-resolution photoelectron spectra obtained from ferromagnetic Ni (295°K, $0.47T_C$) and paramagnetic Ni (678°K, $1.07T_C$) gave no evidence of a significant change in the amplitude nor of a change in the position of the $d$-electron peak near the high-energy cutoff of the EDC within the experimental uncertainty of ± 0.05 eV. High-temperature EDC were obtained from continuously heated Ni single crystals and electron-gun-evaporated films, using a screened-emitter energy analyzer. These results are compared to related experiments, and it is concluded that the band model of magnetism does not adequately explain Ni photoemission and optical experiments.