Insight into spin transport in oxide heterostructures from interface-resolved magnetic mapping.

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At interfaces between complex oxides, electronic, orbital and magnetic reconstructions may produce states of matter absent from the materials involved, offering novel possibilities for electronic and spintronic devices. Here we show that magnetic reconstruction has a strong influence on the interfacial spin selectivity, a key parameter controlling spin transport in magnetic tunnel junctions. In epitaxial heterostructures combining layers of antiferromagnetic LaFeO_3 (LFO) and ferromagnetic La_0.7Sr_0.3MnO_3 (LSMO), we find that a net magnetic moment is induced in the first few unit planes of LFO near the interface with LSMO. Using X-ray photoemission electron microscopy, we show that the ferromagnetic domain structure of the manganite electrodes is imprinted into the antiferromagnetic tunnel barrier, endowing it with spin selectivity. Finally, we find that the spin arrangement resulting from coexisting ferromagnetic and antiferromagnetic interactions strongly influences the tunnel magnetoresistance of LSMO/LFO/LSMO junctions through competing spin-polarization and spin-filtering effects.
© 2015 Macmillan Publishers Limited. We acknowledge financial support from the European Research Council (ERC Advanced Grant FEMMES, No. 267579) and the Labex NanoSaclay project FIRET. The ALICE project is supported by the BMBF Contract No. 05K10PC2. The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007–2013) under grant agreement no. 226716. Work at UCM was supported by grants MAT2011-27470-C02 and Consolider Ingenio 2010—CSD2009- 00013 (Imagine), by CAM through grant S2009/MAT-1756 (Phama) and by the ERC starting Investigator Award, grant #239739 STEMOX. Microscopy at ORNL (M.V.) was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. We thank N.M. Nemes and M. Garcı´a- Herna´ndez for collaboration and assistance with the preliminary magnetic characterization of the LSMO/LFO structures and V. Garcia for his constructive comments. Author contributions: F.Y.B., J.S., A.B. and M.B. designed and conceived the experiment. F.Y.B. and A.R.-C. were involved in sample growth and characterization. F.Y.B. and C.V were involved in lithography process and transport measurements. S.V. conceived the synchrotron experiments. F.Y.B., S.V., R.A., J.T., A.A.U¨ . and A.R.-C. were involved in synchrotron measurements and data analysis. M.V. and S.J.P. performed electron microscopy. M.N.G. and M.B performed tunnelling magneto-resistance simulations. F.Y.B., M.N.G., C.V., Z.S., C.L., J.E.V., J.S., A.B. and M.B analyzed the data and discussed the manuscript. F.Y.B. and M.B. wrote the article with inputs from all co-authors. Competing financial interests: The authors declare no competing financial interests.
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