Temperature-dependent spin-resolved electronic structure of EuO thin films

The electronic structure of the ferromagnetic semiconductor EuO is investigated by means of spin- and angle-resolved photoemission spectroscopy (spin-ARPES) and density functional theory. EuO exhibits unique properties of hosting both weakly dispersive nearly fully polarized Eu 4 f bands, as well as O 2p levels indirectly exchange-split by the interaction with Eu nearest neighbors. Our temperature-dependent spin-ARPES data directly demonstrate the exchange splitting in O 2p and its vanishing at the Curie temperature. Our calculations with a Hubbard U term reveal a complex nature of the local exchange splitting on the oxygen site and in conduction bands. We discuss the mechanisms of indirect exchange in the O 2p levels by analyzing the orbital resolved band characters in ferromagnetic and antiferromagnetic phases. The directional effects due to spin-orbit coupling are predicted theoretically to be significant in particular in the Eu 4 f band manifold. The analysis of the shape of spin-resolved spectra in the Eu 4 f spectral region reveals signatures of hybridization with O 2p states, in agreement with the theoretical predictions. We also analyze spectral changes in the spin-integrated spectra throughout the Curie temperature, and demonstrate that they derive from both the magnetic phase transition and effects due to sample aging, unavoidable for this highly reactive material.

Automated summary

The electronic structure of the ferromagnetic semiconductor EuO has been investigated using spin- and angle-resolved photoemission spectroscopy (spin-ARPES) and density functional theory. EuO exhibits unique properties of hosting both weakly dispersive nearly fully polarized Eu 4 f bands and O 2p levels indirectly exchange-split by the interaction with Eu nearest neighbors. The study sheds light on the mechanisms of indirect exchange in the O 2p levels and predicts significant directional effects due to spin-orbit coupling in the Eu 4 f band manifold.