Magnetic Exciton of EuS Revealed by Resonant Inelastic X-Ray Scattering

Area of Science:

• Condensed Matter Physics
• Materials Science
• X-ray Spectroscopy

Background:

• Europium sulfide (EuS) exhibits complex electronic properties relevant to magnetism.
• Understanding electron-hole interactions is crucial for novel electronic materials.
• Previous optical studies suggested the presence of magnetic excitons in EuS.

Purpose of the Study:

• To investigate the electronic excitations in EuS using valence-to-core resonant inelastic x-ray scattering (RXS).
• To provide direct experimental evidence for the existence of magnetic excitons in EuS.
• To elucidate the nature and origins of different excitation channels in EuS.

Main Methods:

• Valence-to-core resonant inelastic x-ray scattering (RXS) measurements.
• Spectroscopy performed at the L3 edge of Europium (Eu).
• Analysis of emitted photon spectra to identify electronic transitions.

Main Results:

• Two distinct sets of electronic excitations were observed in EuS.
• Delocalized excitations involve S 3p holes and Eu 5d band electrons (dipole-allowed 5d→2p emission).
• Localized excitations correspond to Eu 4f holes and bound Eu 5d electrons, identified as magnetic excitons (quadrupole-allowed 4f→2p emission).

Conclusions:

• The study provides the first direct experimental evidence for magnetic excitons in EuS.
• Both delocalized and localized excitation channels contribute significantly to the RXS spectra.
• The findings validate theoretical models and offer insights into the electronic structure of magnetic materials.