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Atomic-resolution studies of epitaxial strain release mechanisms in La_(1.85)Sr_(0.15)CuO_(4)/La_(0.67)Ca_(0.33)MnO_(3) superlattices

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Biskup Zaja, Nevenko and Das, S. and González-Calbet, J. M. and Bernhard, C. and Varela del Arco, María (2015) Atomic-resolution studies of epitaxial strain release mechanisms in La_(1.85)Sr_(0.15)CuO_(4)/La_(0.67)Ca_(0.33)MnO_(3) superlattices. Physical review B, 91 (20). ISSN 1098-0121

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Official URL: http://dx.doi.org/10.1103/PhysRevB.91.205132


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Abstract

In this paper we present an atomic-resolution electron microscopy study of superlattices (SLs) where the colossal
magnetoresistant manganite La_(0.67)Ca_(0.33)MnO_(3) (LCMO) and the high critical temperature superconducting
cuprate La_(1.85)Sr_(0.15)CuO_(4 (LSCO) are combined. Although good quality epitaxial growth can be achieved, both the choice of substrate and the relatively large lattice mismatch between these materials (around 2%) have a significant impact on the system properties [Phys. C 468, 991 (2008); Nature (London) 394, 453 (1998)]. Our samples, grown by pulsed laser deposition, are epitaxial and exhibit high structural quality. By means of cutting-edge electron microscopy and spectroscopy techniques we still find that the epitaxial strain is accommodated by a combination of defects, such as interface steps and antiphase boundaries in the manganite. These defects result in inhomogeneous strain fields through the samples. Also, some chemical unhomogeneities are detected, up to
the point that novel phases nucleate. For example, at the LCMO/LSCO interface the ABO3-type manganite adopts a tetragonal LSCO-like structure forming localized layers that locally resemble the composition of La_(2/3)Ca_(4/3)MnO_(4). Structural distortions are detected in the cuprate as well, which may extend over lateral distances of several unit cells. Finally, we also analyze the influence of the substrate-induced strain by examining superlattices grown on two different substrates: (LaAlO_(3))_(0.3)(Sr_(2)AlTaO_(6))_(0.7) (LSAT) and LaSrAlO_(4) (LSAO). We observe that SLs grown on LSAT, which are nonsuperconducting, present reduced values of the c axis compared to superlattices grown on LSAO (which are fully superconducting). This finding points to the fact that the proper distance between copper planes in LSCO is essential in obtaining superconductivity in cuprates.


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Additional Information:

© 2015 American Physical Society. We thank A. Lupini for the DM script used for quantification of the lattice constants (Fig. 4) and M. Watanabe for the plug-in for PCA. M.V. acknowledges discussions with J. Mitchell. N.B. and the electron microscopy performed at the Centro Nacional de Microscopia Electrónica (UCM) were sponsored by the ERC Starting Investigator Award No. STEMOX#239739. The research at the University of Fribourg was supported by the Schweizer Nationalfonds (SNF) Grants No. 200020-140225 and No. 200020-153660.

Uncontrolled Keywords:Electron-energy-loss; Critical-temperature; Crystal-structure; Superconductivity; Oxides; La_(1.85)Sr_(0.15)CuO_(4); Perovskite; Dependence; Pressure; Spectra.
Subjects:Sciences > Physics > Electricity
Sciences > Physics > Electronics
ID Code:33037
Deposited On:10 Sep 2015 08:54
Last Modified:10 Dec 2018 14:57

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