Resumen: We report on magnetotransport properties on La0.7Sr0.3MnO3/MgO/Fe tunnel junctions grown epitaxially on top of (001)-oriented SrTiO3 substrates by sputtering. It is shown that the magnetoresistive response depends critically on the MgO/Fe interfacial properties. The appearance of an FeOX layer by the interface destroys the ¿1 symmetry filtering effect of the MgO/Fe system and only a small negative tunneling magnetoresistance (TMR) (~-3%) is measured. However, in annealed samples a switchover from positive TMR (~+25% at 70 K) to negative TMR (~-1%) is observed around 120 K. This change is associated with the transition from semiconducting at high T to insulating at low T taking place at the Verwey transition (TV~120K) in Fe3O4, thus suggesting the formation of a very thin slab of magnetite at the MgO/Fe interface during annealing treatments. These results highlight the relevance of interfacial properties on the tunneling conduction process and how it can be substantially modified through appropriate interface engineering. Idioma: Inglés DOI: 10.1103/PhysRevB.92.094428 Año: 2015 Publicado en: Physical Review B 92, 9 (2015), 094428 [7 pp] ISSN: 1098-0121 Factor impacto JCR: 3.718 (2015) Categ. JCR: PHYSICS, CONDENSED MATTER rank: 16 / 67 = 0.239 (2015) - Q1 - T1 Factor impacto SCIMAGO: 2.377 - Electronic, Optical and Magnetic Materials (Q1) - Condensed Matter Physics (Q1)