AUTHOR=Miyazaki Hidetoshi , Hajiri Tetsuya , Matsunami Masaharu , Inukai Manabu , Ito Takahiro , Kimura Shin-ichi 

TITLE=Observation of Thickness-Dependent Exchange Interaction in EuO Ultrathin Films

JOURNAL=Frontiers in Nanotechnology

VOLUME=Volume 4 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/nanotechnology/articles/10.3389/fnano.2022.872717

DOI=10.3389/fnano.2022.872717

ISSN=2673-3013

ABSTRACT=The electronic structure of single crystalline EuO (100) ultrathin films, together with their exchange splitting energy (delta-E_EX) and ferro-magnetic phase transition temperature (TC), was investigated by temperature- and thickness-dependent angle-resolved photoemission spectroscopy. Both delta-E_EX and TC decreased monotonically with decreasing film thickness. The band shift showed an opposite thickness dependence at the  and X points, reflecting the balance of the hybridization between the Eu 4f and O 2p states (super-exchange interaction) and between the Eu 4f-O 2p and Eu 5d states (indirect-exchange interaction). The observed transition from an indirect energy gap in the bulk to a direct gap in the ultrathin films of the ferromagnetic semiconductor EuO could be potential in future spintronics devices.