Thermodynamic conditions during growth determine the magnetic anisotropy in epitaxial thin-films of La0.7_{0.7}Sr0.3_{0.3}MnO3_{3}

The suitability of a particular material for use in magnetic devices is determined by the process of magnetization reversal/relaxation, which in turn depends on the magnetic anisotropy. Therefore, designing new ways to control magnetic anisotropy in technologically important materials is highly desirable. Here we show that magnetic anisotropy of epitaxial thin-films of half-metallic ferromagnet La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ (LSMO) is determined by the proximity to thermodynamic equilibrium conditions during growth. We performed a series of X-ray diffraction and ferromagnetic resonance (FMR) experiments in two different sets of samples: the first corresponds to LSMO thin-films deposited under tensile strain on (001) SrTiO$_{3}$ by Pulsed Laser Deposition (PLD; far from thermodynamic equilibrium); the second were deposited by a slow Chemical Solution Deposition (CSD) method, under quasi-equilibrium conditions. Thin films prepared by PLD show a in-plane cubic anisotropy with an overimposed uniaxial term. A large anisotropy constant perpendicular to the film plane was also observed in these films. However, the uniaxial anisotropy is completely suppressed in the CSD films. The out of plane anisotropy is also reduced, resulting in a much stronger in plane cubic anisotropy in the chemically synthesized films. This change is due to a different rotation pattern of MnO$_{6}$ octahedra to accomodate epitaxial strain, which depends not only on the amount of tensile stress imposed by the STO substrate, but also on the growth conditions. Our results demonstrate that the nature and magnitude of the magnetic anisotropy in LSMO can be tuned by the thermodynamic parameters during thin-film deposition.Comment: 6 pages, 8 Figure

Thermodynamic conditions during growth determine the magnetic anisotropy in epitaxial thin-films of La0.7Sr0.3MnO3

et al.The suitability of a particular material for use in magnetic devices is determined by the process of magnetization reversal/relaxation, which in turn depends on the magnetic anisotropy. Therefore, designing new ways to control magnetic anisotropy in technologically important materials is highly desirable. Here we show that magnetic anisotropy of epitaxial thin-films of half-metallic ferromagnet LaSrMnO (LSMO) is determined by the proximity to thermodynamic equilibrium conditions during growth. We performed a series of x-ray diffraction and ferromagnetic resonance (FMR) experiments in two different sets of samples: the first corresponds to LSMO thin-films deposited under tensile strain on (0 0 1) SrTiO by pulsed laser deposition (PLD; far from thermodynamic equilibrium); the second were deposited by a slow chemical solution deposition (CSD) method, under quasi-equilibrium conditions. Thin films prepared by PLD show fourfold in-plane magnetic anisotropy, with an overimposed uniaxial term. However, the uniaxial anisotropy is completely suppressed in the CSD films. This change is due to a different rotation pattern of MnO octahedra to accommodate epitaxial strain, which depends not only on the amplitude of tensile stress imposed by the STO substrate, but also on the growth conditions. Our results demonstrate that the nature and magnitude of the magnetic anisotropy in LSMO can be tuned by the thermodynamic parameters during thin-film deposition.This work was supported by the European Research Council (ERC StG-259082, 2DTHERMS), Xunta de Galicia (2012-Projet No. CP072) and by the Ministry of Science of Spain (Project No. MAT2013-44673-R). JMVF also acknowledges the same organization for an FPI grant. EW and JM thank UNCuyo Argentina for Grant No C011.Peer Reviewe

Monolithic integration of functional oxides in silicon by chemical solution deposition

6-10 Avril 2015International audienceno abstrac

Monolitic integration of functional oxides on silicon by chemical solution deposition

6-9 April 2015International audienceIn the past years, great efforts have been devoted to combine the functionality of oxides with the performances of semiconductor platforms for the development of novel and more efficient device applications. However, further incorporation of functional oxide nanostructures as active materials in electronics critically depends on the ability to integrate crystalline metal oxides into silicon structures [1]. In this regard, the presented work takes advantage of all the benefits of soft chemistry to overcome the main challenges for the monolithic integration of novel nanostructured functional oxide materials on silicon including (i) epitaxial piezoelectric α-quartz thin films with tunable textures on silicon wafers [2] and (ii) ferromagnetic La0.7Sr0.3MnO3 (LSMO) thin films epitaxially grown on (100)-silicon at low temperature. Importantly, piezoelectric quartz growth mechanism is governed by a thermally activated devitrification of the native amorphous silica surface layer assisted by a heterogeneous catalysis under atmospheric conditions driven by alkaline earth cations present in the precursor solution. Quartz films are made of perfectly oriented individual crystallites epitaxially grown on (100) face of Si substrate with a controlled porosity after using templating agents [3]. Moreover, a quantitative study of the converse piezoelectric effect of quartz thin films through piezoresponse force microscopy shows that the piezoelectric coefficient d33 is between 1.5 and 3.5 pm/V which is in agreement with the 2.3 pm/V of the quartz single crystal d11. Epitaxial LSMO thin films synthesis, involves the use of polymer assisted deposition (PAD) process [4] combined with the controlled epitaxial growth of SrTiO3 buffer layer grown by molecular beam epitaxy (MBE) at the silicon surface, which allowed LSMO thin films to stabilize and crystallize at low temperature. All together, the methodology presented here exhibits a great potential and offers a pathway to design novel oxide compounds on silicon substrates by chemical routes with unique optical, electric, or magnetic properties. [1] A. Carretero-Genevrier et al. Nanoscale, 20, 892-897. (2014). [2] A. Carretero-Genevrier et al. Science, 20, 892-897. (2013). [3] G.L. Drisko et al. Adv.Funct.Mater. 24, 5494–5502 (2014) [4] Q. X. Jia, et al. Nature Materials 3, 529 (2004

Spontaneous cationic ordering in chemicalsolution- grown La2CoMnO6 double perovskite thin films

Double perovskite oxides are of interest because of their electric, magnetic, and elastic properties; however, these properties are strongly dependent on the ordered arrangement of cations in the double perovskite structure. Therefore, many efforts have been made to improve the level of cationic ordering to obtain optimal properties while suppressing antisite defect formation. Here, epitaxial double perovskite La2CoMnO6 thin films were grown on top of (001)-STO oriented substrates by a polymer-assisted deposition chemical solution approach. Confirmation of the achievement of full Co/Mn cationic ordering was found by scanning transmission electron microscopy (STEM) measurements; EELS maps indicated the ordered occupancy of B–B′ sites by Co/Mn cations. As a result, optimal magnetic properties (Msat ≈ 6 µB/f.u. and Tc ≈ 230 K) are obtained. We show that the slow growth rates that occur close to thermodynamic equilibrium conditions in chemical solution methods represent an advantageous alternative to physical deposition methods for the preparation of oxide thin films in which complex cationic ordering is involved.We acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-0496), COACHSUPENERGY project (MAT2014-51778-C2-1-R) and MAT2015-71664-R, cofinanced by the European Regional Development Fund. Support from the European Union′s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie grant agreement no. 645658 (DAFNEOX Project) is also acknowledged. H.W. acknowledges financial support from the China Scholarship Council (CSC). J.G. also acknowledges the Ramon y Cajal program (RYC-2012-11709). The STEM–EELS analysis was sponsored by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. The authors would like to thank Anna Crespi and Francesc Xavier Campos for assistance with the 3D reciprocal space tomography and reciprocal space map measurements.Peer reviewe