Localized states in advanced dielectrics from the vantage of spin- and symmetry-polarized tunnelling across MgO

• Published in: Nature communications 2014-08, Vol.5 (1), p.4547-4547, Article 4547
• Main Authors: Schleicher, F., Halisdemir, U., Lacour, D., Gallart, M., Boukari, S., Schmerber, G., Davesne, V., Panissod, P., Halley, D., Majjad, H., Henry, Y., Leconte, B., Boulard, A., Spor, D., Beyer, N., Kieber, C., Sternitzky, E., Cregut, O., Ziegler, M., Montaigne, F., Beaurepaire, E., Gilliot, P., Hehn, M., Bowen, M.
• Format: Article
• Language: English
• Subjects: 639/766/119/1001; 639/766/25; Condensed Matter; Humanities and Social Sciences; Materials Science; multidisciplinary; Physics; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms5547

Research on advanced materials such as multiferroic perovskites underscores promising applications, yet studies on these materials rarely address the impact of defects on the nominally expected materials property. Here, we revisit the comparatively simple oxide MgO as the model material system for spin-polarized solid-state tunnelling studies. We present a defect-mediated tunnelling potential landscape of localized states owing to explicitly identified defect species, against which we examine the bias and temperature dependence of magnetotransport. By mixing symmetry-resolved transport channels, a localized state may alter the effective barrier height for symmetry-resolved charge carriers, such that tunnelling magnetoresistance decreases most with increasing temperature when that state is addressed electrically. Thermal excitation promotes an occupancy switchover from the ground to the excited state of a defect, which impacts these magnetotransport characteristics. We thus resolve contradictions between experiment and theory in this otherwise canonical spintronics system, and propose a new perspective on defects in dielectrics. Crystal defects and impurities can have a profound effect on the operation of electronic and spintronic devices. Schleicher et al. now show how such defects can influence the temperature dependence of the magnetoresistance of magnesium-oxide-based magnetic tunnel junctions.