‘‘Collapsing’’ versus ‘‘noncollapsing’’ empty band states in iron (invited; abstract)

摘要

We report on the behavior of unoccupied exchange split bands in iron on approaching the Curie temperature at different points in the Brillouin zone. We use spin‐polarized isochromat spectroscopy, which allows to identify the spin‐character of the bands. Near the H point in bcc Fe we observe minority and majority states to merge with increasing temperature, providing evidence for a ‘‘collapsing’’ band state at this point of the Brillouin zone. The flat empty minority band of Fe is sampled at two other points in k space by using different crystal surfaces and/or different angles of incidence. At these locations the energetic position of the minority peak remains unchanged, indicating the existence of ‘‘noncollapsing’’ band states. These findings are compared to the predictions of the ‘‘local band’’ theory and the ‘‘disordered local moment’’ theory.