Spin-Dependent On-Site Electron Correlations and Localization in Itinerant Ferromagnets

Abstract

Spin selectivity in angle-resolved Auger photoelectron coincidence spectroscopy (AR-APECS) is used to probe electron correlation in ferromagnetic thin films. In particular, exploiting the AR-APECS capability to discriminate Auger electron emission events characterized by valence hole pairs created either in the high or in the low total spin state, a strong correlation effect in the Fe M(2,3)VV Auger line shape (measured in coincidence with the Fe 3p photoelectrons) of Fe/Cu(001) thin films is detected and ascribed to interactions within the majority spin subband. Such an assignment follows from a close comparison of the experimental AR-APECS line shapes with the predictions of a model based on spin polarized density functional theory and the Cini-Sawatzky approach.

Fingerprints of entangled spin and orbital physics in itinerant ferromagnets via angle-resolved resonant photoemission

“…These more localized valence flip excitations are then transferred to the photoelectron. The visible orbital flip effect is thus a manifestation of a different correlation in the two bands with different spin, established recently on a quantitative basis by experimental and theoretical studies on Auger emission 26 , and of different orbital character, as earlier suggested 70 . Orbitals appear nearly as quenched far from E F , where only spin flip excitations are clear, while spin and orbital degrees of freedom are entangled and both active at low energy.…”

Nonlocal electron correlations in an itinerant ferromagnet

“…Consequently, such localization leads to electronic states that do not disperse in energy over the reciprocal space. Examples are found in compounds of the heavy rare earth elements where strongly localized f-electron states are responsible for the weakly dispersing heavy fermion bands but also for the core levels of the elemental ferromagnets, for which spin-dependent renormalization was firstly observed 28 , 29 . By contrast, the 3d-electron states responsible for band ferromagnetism are only weakly localized, and characterized by a sizeable energy dispersion over the BZ.…”

Core-resonant double photoemission from palladium films

“…For this material U W / 0.8 ≈ hence its Auger lineshape is in the intermediate region between a band-like and atomic like behavior. The complexity of the Auger spectra can be reduced by electron coincidence spectroscopy and significant experimental advances have been made in the past [6,[8][9][10][11][12][13].…”