@article{oai:nagoya.repo.nii.ac.jp:00018679,
 author = {Miyazaki, H. and Ito, T. and Im, H. J. and Yagi, S. and Kato, M. and Soda, K. and Kimura, S.},
 journal = {Physical Review Letters},
 month = {Jun},
 note = {We measured the temperature-dependent three-dimensional angle-resolved photoemission spectra of EuO (100) thin film, a typical Heisenberg ferromagnetic semiconductor, to investigate the essential origin of the ferromagnetic transition. We observed sizable energy dispersion and large binding-energy shift of the Eu 4f state below the Curie temperature only near the Γ and X points, despite the expected Heisenberg-type local magnetism. The band dispersion and temperature dependence of the Eu 4f state indicates that the indirect exchange and superexchange interactions have strong momentum dependence. The observed temperature-dependent energy shift of the 4f state is the essential origin of the magnetism of EuO.},
 pages = {227203--227203},
 title = {Direct Observation of Momentum-Dependent Exchange Interaction in a Heisenberg Ferromagnet},
 volume = {102},
 year = {2009}
}