CeMnNi4 exhibits an unusually large spin polarization, but its origin has baffled researchers for more than a decade. We use bulk sensitive hard x-ray photoelectron spectroscopy (HAXPES) and density functional theory based on the Green's function technique to demonstrate the importance of electron-electron correlations of both the Ni 3d (UNi) and Mn 3d (UMn) electrons in explaining the valence band of this multiply correlated material. We show that Mn-Ni antisite disorder as well as UNi play a crucial role in enhancing its spin polarization: Antisite disorder broadens a Ni 3d minority-spin peak close to the Fermi level (EF), while an increase in UNi shifts it toward EF, both leading to a significant increase of minority-spin states at EF. Furthermore, the rare occurrence of a valence state transition between the bulk and the surface is demonstrated highlighting the importance of HAXPES in resolving the electronic structure of materials unhindered by surface effects.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics