Interface properties of magnetic tunnel junction La0.7Sr0.3MnO3/SrTiO3 superlattices studied by standing-wave excited photoemission spectroscopy

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Gray, A.X. and Papp, C. and Balke, B. and Yang, S.-H. and Huijben, M. and Rotenberg, E. and Bostwick, A. and Ueda, S. and Yamashita, Y. and Kobayashi, K. and Gullikson, E.M. and Kortright, J.B. and Groot de, F.M.F. and Rijnders, G. and Blank, D.H.A. and Ramesh, R. and Fadley, C.S. (2010) Interface properties of magnetic tunnel junction La0.7Sr0.3MnO3/SrTiO3 superlattices studied by standing-wave excited photoemission spectroscopy. Physical Review B: Condensed matter and materials physics, 82 (20). p. 205116. ISSN 1098-0121

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Abstract:The chemical and electronic-structure profiles of magnetic tunnel junction (MTJ) La0.7Sr0.3MnO3/SrTiO3 (LSMO/STO) superlattices have been quantitatively determined via soft and hard x-ray standing-wave excited photoemission, x-ray absorption and x-ray reflectivity, in conjunction with x-ray optical and core-hole multiplet theoretical modeling. Epitaxial superlattice samples consisting of 48 and 120 bilayers of LSMO and STO, each nominally four unit cells thick, and still exhibiting LSMO ferromagnetism, were studied. By varying the incidence angle around the superlattice Bragg condition, the standing wave was moved vertically through the interfaces. By comparing experiment to x-ray optical calculations, the detailed chemical profile of the superlattice and its interfaces was quantitatively derived with angstrom precision. The multilayers were found to have a small ∼6% change in periodicity from top to bottom. Interface compositional mixing or roughness over ∼6 Å was also found, as well as a significant change in the soft x-ray optical coefficients of LSMO near the interface. The soft x-ray photoemission data exhibit a shift in the position of the Mn 3p peak near the interface, which is not observed for Mn 3s. Combined with core-hole multiplet theory incorporating Jahn-Teller distortion, these results indicate a change in the Mn bonding state near the LSMO/STO interface. Our results thus further clarify the reduced (MTJ) performance of LSMO/STO compared to ideal theoretical expectations.

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Copyright:© 2010 The American Physical Society
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Science and Technology (TNW)
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Link to this item:http://purl.utwente.nl/publications/75244
Official URL:http://dx.doi.org/10.1103/PhysRevB.82.205116
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