Abstract
The magnetic and electrical properties of complex oxide thin films are closely related to the phase stability and cation ordering, which demands that we understand the process-structure-property relationships microscopically in functional materials research. Here we study multiferroic thin films of double-perovskite La2NiMnO6 epitaxially grown on SrTiO3, KTaO3, LaAlO3 and DyScO3 substrates by pulsed laser deposition. The effect of epitaxial strains imposed by the substrate on the microstructural properties of La2NiMnO6 has been systematically investigated by means of advanced electron microscopy. It is found that La2NiMnO6 films under tensile strain exhibit a monoclinic structure, while under compressive strain the crystal structure of La2NiMnO6 films is rhombohedral. In addition, by optimizing the film deposition conditions a long-range ordering of B-site cations in La2NiMnO6 films has been obtained in both monoclinic and rhombohedral phases. Our results not only provide a strategy for tailoring phase stability by strain engineering, but also shed light on tuning B-site ordering by controlling film growth temperature in double-perovskite La2NiMnO6 films.
Highlights
Double-perovskite multiferroic La2NiMnO6 (LNMO) received much attention in recent decades due to its abundant magnetoresistance, magnetocapacitance[1,2,3] and dielectric properties[2,4,5]
It should be noted that the weak reflections appear in the selected area electron diffraction (SAED) patterns of LNMO film grown on STO and DSO substrates (See Figure S1 of the Supplemental Material)
It should be mentioned that monoclinic LNMO (P21/n) and orthorhombic LNMO (Pbnm) display structural similarity, which leads to impossible to discern them based on X-ray measurement[17] and SAED patterns
Summary
Double-perovskite multiferroic La2NiMnO6 (LNMO) received much attention in recent decades due to its abundant magnetoresistance, magnetocapacitance[1,2,3] and dielectric properties[2,4,5]. It is noted that in comparison with the significant studies on the synthesis and properties of bulk materials[1,6,13,18,36,37], there was a lack of information on the ordering of B-site in double-perovskite films related to the growth parameters and the epitaxial strain induced structure evolution. By applying these microscopic analytical techniques, we have systematically investigated phase structure of LNMO films affected by the epitaxial strain and misfit strain relaxation of LNMO films grown on different perovskite-type substrates including KTaO3 (KTO), DyScO3 (DSO), SrTiO3 (STO) and LaAlO3 (LAO). We hope that the present studies would promote the understanding of the effect of the growth process on the structural and physical properties in double-perovskite LNMO films
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