Graded orbital occupation near interfaces in aLa2NiO4−La2CuO4superlattice
| Autor: | Ivan Bozovic, Gennady Logvenov, Oshri Pelleg, Yingchun Zhu, Serban Smadici, J. C. T. Lee, Peter Abbamonte, J. Morales |
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| Rok vydání: | 2011 |
| Předmět: | |
| Zdroj: | Physical Review B. 84 |
| ISSN: | 1550-235X 1098-0121 |
| DOI: | 10.1103/physrevb.84.155411 |
| Popis: | X-ray absorption spectroscopy and resonant soft x-ray reflectivity show a nonuniform distribution of oxygen holes in a ${\mathrm{La}}_{2}{\mathrm{NiO}}_{4}\ensuremath{-}{\mathrm{La}}_{2}{\mathrm{CuO}}_{4}$ (LNO-LCO) superlattice, with excess holes concentrated in the LNO layers. Weak ferromagnetism with ${T}_{c}=160$ K suggests a coordinated tilting of ${\mathrm{NiO}}_{6}$ octahedra, similar to that of bulk LNO. Ni ${d}_{3{z}^{2}\ensuremath{-}{r}^{2}}$ orbitals within the LNO layers have a spatially variable occupation. This variation of the Ni valence near LNO-LCO interfaces is observed with resonant soft x-ray reflectivity at the Ni and Cu L edges, at a reflection suppressed by the symmetry of the structure, and is possible through graded doping with holes, due to oxygen interstitials taken up preferentially by inner LNO layers. Since the density of oxygen atoms in the structure can be smoothly varied with standard procedures, this orbital occupation, robust up to at least 280 K, is tunable. |
| Databáze: | OpenAIRE |
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