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X-ray absorption spectroscopy was used to determine the valence state in La2Co1-xMn1+xO6 (x≈0.23) thin films. We found that in spite of the nonstoichiometry, Co is in a divalent state while Mn ions show a mixed valence state. The relation of this finding with the magnetic properties of the films is discussed. X-ray magnetic circular dichroism measurements prove that magnetic anisotropy originates from Co spin-orbit coupling and it is strain dependent: a strong increase of the angular contribution to the magnetic moment is found when in-plane (out-of-plane) cell parameters get expanded (compressed). This behavior is reproduced by first order perturbation theory calculations. Fil: López-Mir, Laura. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de los Materiales de Barcelona; España Fil: Galceran, Regina. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de los Materiales de Barcelona; España Fil: Herrero Martín, Javier. ALBA Synchrotron Light Source; España Fil: Bozzo, Bernat. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de los Materiales de Barcelona; España Fil: Cisneros-Fernández, José. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de los Materiales de Barcelona; España Fil: Pannunzio Miner, Elisa Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de los Materiales de Barcelona; España Fil: Pomar, Alberto. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de los Materiales de Barcelona; España Fil: Balcells, Lluís. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de los Materiales de Barcelona; España Fil: Martínez, Benjamín. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de los Materiales de Barcelona; España Fil: Frontera, Carlos. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de los Materiales de Barcelona; España

Ferromagnetic insulating La2CoMnO6-ε (LCMO) epitaxial thin films grown on top of SrTiO3 (001) substrates present a strong magnetic anisotropy favoring the out of plane orientation of the magnetization with a large anisotropy field (∼70 kOe for film thickness of about 15 nm). Diminishing oxygen off-stoichiometry of the film enhances the anisotropy. We attribute this to the concomitant shrinkage of the out of plane cell parameter and to the increasing of the tensile strain of the films. Consistently, LCMO films grown on (LaAlO3)0.3(Sr2AlTaO6)0.7 and LaAlO3 substrates (with a larger out-of-plane lattice parameter and compressive stress) display in-plane magnetic anisotropy. Thus, we link the strong magnetic anisotropy observed in LCMO to the film stress: tensile strain favors perpendicular anisotropy and compressive stress favors in plane anisotropy. We also report on the thickness dependence of the magnetic properties. Perpendicular anisotropy, saturation magnetization and Curie temperature are maintained over a large range of film thickness., We acknowledge financial support from the Ministerio de Economia y Competitividad through the “Severo Ochoa” Programme for Centres of Excellence in Research and Development (Grant No. SEV-2015-0496), and Grants No. MAT2012-33207 and No. MAT2015-71664-R. L.L.-M.’s work has been done as a part of her Ph.D. program in physics at Universitat Autonoma de Barcelona.

Galceran, Regina et al., © 2015 American Physical Society. 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 Δ1 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., We acknowledge financial support from the Spanish MINECO through grants (MAT2012-33207, MAT2011-27470-C02, MAT2012-37638 and Consolider Ingenio 2010 - CSD2009-00013 (Imagine)), from CAM through Grant No. S2009/MAT-1756 (Phama) and Basque Government (PI2011-1). Financial support from EC through FEDER program and Marie Curie Actions (256470-ITAMOSCINOM) is also acknowledged. C.M.B. thanks the Spanish MINECO for the financial support through the RyC program

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY)., There is increasing evidence supporting the strong potential of twin walls in ferroic materials as distinct, spatially tunable, functional elements in future electronic devices. Here, we report an increase of about one order of magnitude in conductivity and more robust magnetic interactions at (100)-type twin walls in La0.7Sr0.3MnO3 thin films. The nature and microscopic origin of such distinctive behavior is investigated by combining conductive, magnetic, and force modulation scanning force microscopies with transmission electron microscopy techniques. Our analyses indicate that the observed behavior is due to a severe compressive strained state within an ∼1nm slab of material centered at the twin walls, promoting stronger Mn 3d-O2p orbital overlapping leading to a broader bandwidth and enhanced magnetic interactions., This research was sponsored by the Spanish MINECO (Grants No. MAT2011- 29081-C02, No. MAT2012-33207, and No. MAT2013-47869-C4-1-P) projects. We also acknowledge financial aid from the Generalitat de Catalunya (2014 SGR 501). N.B. and F.S. also acknowledge funding from the European Union Seventh Framework Programme under Grant Agreement No. 312483-ESTEEM2 (Integrated Infrastructure Initiative I3) for providing access to aberration corrected electron microscopes at CEMES (Toulouse) and LPS (Orsay). R.G. and N.B. thank the Spanish MINECO for financial support through the FPI program. F.S. acknowledges support from the Labex (Excellence Laboratory) NEXT through a visiting scientist fellowship at CEMES (Toulouse, France).