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arXiv · 1710.08535

The Onset of Phase Separation in the Double Perovskite Oxide La$_2$MnNiO$_6$

Steven R. Spurgeon·Peter V. Sushko·Arun Devaraj·Yingge Du·Timothy Droubay·Scott A. Chambers
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Abstract

Identification of kinetic and thermodynamic factors that control crystal nucleation and growth represents a central challenge in materials synthesis. Here we report that apparently defect-free growth of La$_2$MnNiO$_6$ (LMNO) thin films supported on SrTiO$_3$ (STO) proceeds up to $1-5$ nm, after which it is disrupted by precipitation of NiO phases. Local geometric phase analysis and ensemble-averaged X-ray reciprocal space mapping show no change in the film strain away from the interface, indicating that mechanisms other than strain relaxation induce the formation of the NiO phases. $Ab \, initio$ simulations suggest that oxygen vacancies become more likely with increasing thickness, due to the electrostatic potential build-up associated with the polarity mismatch at the film-substrate interface, this, in turn, promotes the formation of Ni-rich regions. These results suggest that the precipitate-free region could be extended further by increasing the oxygen chemical potential through the use of an elevated oxygen pressure or by incorporating electron redistributing dopants to suppress the built-in potential.

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Steven R. Spurgeon, Peter V. Sushko, Arun Devaraj, Yingge Du, Timothy Droubay, Scott A. Chambers. 2017-10-23. The Onset of Phase Separation in the Double Perovskite Oxide La$_2$MnNiO$_6$. https://doi.org/10.1103/physrevb.97.134110

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