Abstract
We present a single-step route to generate ordered nanocomposite thin films of secondary phase inclusions (Mn3O4) in a pristine perovskite matrix (LaMnO3) by taking advantage of the complex phase diagram of manganese oxides. We observed that in samples grown under vacuum growth conditions from a single LaMnO3 stoichiometric target by Pulsed Laser Deposition, the most favourable mechanism to accommodate Mn2+ cations is the spontaneous segregation of self-assembled wedge-like Mn3O4 ferrimagnetic inclusions inside a LaMnO3 matrix that still preserves its orthorhombic structure and its antiferromagnetic bulk-like behaviour. A detailed analysis on the formation of the self-assembled nanocomposite films evidences that Mn3O4 inclusions exhibit an epitaxial relationship with the surrounding matrix that it may be explained in terms of a distorted cubic spinel with slight (~9o) c-axis tilting. Furthermore, a Ruddlesden-Popper La2MnO4 phase, helping to the stoichiometry balance, has been identified close to the interface with the substrate. We show that ferrimagnetic Mn3O4 columns influence the magnetic and transport properties of the nanocomposite by increasing its coercive field and by creating local areas with enhanced conductivity in the vicinity of the inclusions.
Highlights
The large choice in chemical elements in either A- and B-site of the perovskite structure allows tailoring many parameters including lattice constants, electronic band structures, magnetic interactions, and more
We report on the spontaneous formation of regular vertically aligned nanocolumns composed of manganese oxide embedded in antiferromagnetic LaMnO3 matrix grown by pulsed laser deposition (PLD) on (001)-oriented single crystal perovskite substrates of LaAlO3 (LAO) and SrTiO3 (STO)
Films grown in vacuum conditions exhibit a clear ordered nanocomposite surface, as evidenced by Scanning Electron Microscopy (SEM) images either on STO or LAO substrates
Summary
The large choice in chemical elements in either A- and B-site of the perovskite structure allows tailoring many parameters including lattice constants, electronic band structures, magnetic interactions, and more. Manganese based oxides display a huge range of properties from total spin polarization and colossal magnetoresistance to multiferroicity, with potential use from active electrodes in electronic devices to sensors and magnetic memories. Nanostructured thin films widen their application range as their final functional properties are determined by the very active role of interfaces and surfaces which may be efficiently modified by strain relaxation mechanisms [1,2,3,4]. In addition to standard heterointerfaces in layered structures, new strategies have been developed to increase the surface to volume ratio and to enhance interfacial effects. In this sense, vertically heteroepitaxial nanocomposites (VHN) provide
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