LDA + Negative U Solves a Puzzle of too Large Calculated Magnetic Moment in Iron-based Superconductor LaFeAsO_{1-x}F_x
| Autor: | Nakamura, H., Hayashi, N., Nakai, N., Machida, M. |
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| Rok vydání: | 2008 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | A puzzle in the iron-based superconductor LaFeAsO_{1-x}F_x is that the magnetic moment obtained by first-principle electronic structure calculations is unexpectedly much larger than the experimentally observed one. For example, the calculated value is ~ 2.0 \mu_B in the mother compound, while it is ~ 0.3 \mu_B in experiments. We find that the puzzle is solved within the framework LDA + U by expanding the U value into a slightly negative range. We show U dependence of the obtained magnetic moment in both the undoped x=0.0 and doped x = 0.125. These results reveal that the magnetic moment is drastically reduced when entering to the slightly negative range of U. Moreover, the negative U well explains other measurement data, e.g., lattice constants and electronic DOS at the Fermi level. We discuss possible origins of the negative U in these compounds. Comment: 5 pages, 4 figures |
| Databáze: | arXiv |
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