The preparation of cation-ordered thin films of correlated oxides is of great interest for both fundamental and applied research. The scientific long-term vision is strongly motivated by the perspective of studying electronic correlations in condensed matter without the presence of chemical or quenched disorder. A promising material platform provides double perovskite A2BB’O6 bulk samples with different types of B/B’ ordering. However, the growth of A- and/or B-site-ordered correlated oxide thin films is known to be a challenging task. In this review, we evaluate the growth of double perovskite A2BB’O6 thin films by means of well-elaborated physical vacuum deposition techniques, such as pulsed laser deposition (PLD) and sputtering and compare them with a close-to-equilibrium growth with the metalorganic aerosol deposition (MAD) technique. The latter was further developed to grow an emergent interfacial double perovskite phase in LaNiO3/LaMnO3 superlattices, and finally, by way of a layer-by-layer route. The growth of La2CoMnO6 films on SrTiO3(111) substrates by sequential deposition of single perovskite layers of LaCoO3/LaMnO3/LaCoO3/… was demonstrated and the film properties were compared to those obtained within the state-of-the art growth mode.

Thin films and heterostructures of hexagonal manganites as promising multiferroic materials have attracted a considerable interest recently. We report structural transformations of high quality epitaxial h-TMO/YSZ(111) films, analyzed by means of various characterization techniques. A phase transition from P63mc to P63mcm structure at TC~800 K was observed by temperature dependent Raman spectroscopy and optical ellipsometry. The latter probing directly electronic system, indicates its modification at the structural phase transition likely due to charge transfer from oxygen to Mn. In situ transmission electron microscopy (TEM) of the lamella samples displayed an irreversible P63mc-P63mcm transformation and vanishing of ferroelectric domains already at 410 K.After the temperature cycling (300K-1300K-300K) the room temperature TEM of h-TMO films revealed an inhomogeneous microstructure, containing ferroelectric and paraelectric nanodomains with P63mc and P63mcm structure, respectively. We point out a strong influence of stress relaxation, induced by temperature and by constrained sample geometry onto the structure and ferroelectricity in strain-stabilized h-TMO thin films.

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cial magnetic and electric phenomena [1][2][3][4] not present in the constituting layers. As the interplay of charge, spin, and lattice degrees of freedom [5] is believed to control phase transitions in bulk correlated materials, their interfacial reconstructions, should serve as guiding mechanisms for emergent phenomena. In particular, the charge transfer (CT)/leakage at the interface [6,7] with a following electronic reconstruction of them was thought to be intimately coupled to the formation of emergent phases. The (LaMnO 3 ) m / (SrMnO 3 ) n (LMO m /SMO n ) SLs can be viewed as one of the most intensively studied oxide heterostructures. [8,9] A longterm interest to them was motivated by the observations of interfacial or emergent ferromagnetism, [10][11][12][13][14] associated with the chemically sharp LMO(top)/SMO(bottom) interfaces. [10] Very recently, we reported a high temperature emergent ferromagnetic phase with Curie temperature T C = 360 K at the SMO/ LMO interfaces, [15] originated from the interfacial CT from the electron-rich LMO to the electron-poor SMO layers.An important but rather rarely addressed question is whether CT can be additionally influenced or controlled by the growth design of SLs, e.g. by tuning the thickness ratio of constituting layers. Garcia-Barriocanal et al. [7] have demonstrated that charge leakage in (LaMnO 3 ) m /(SrTiO 3 ) n (LMO m /STO n ) SLs, indicated by the formation of Ti 3+ within the STO layers, is favored in the SLs with a large thickness ratio LMO 17 /STO 2 and is suppressed when this ratio is small LMO 17 /STO 12 . Moreover, the LMO layers in SLs with a large thickness ratio (17/2) were found to be relaxed but those in SLs with small ratio (7/5) were coherently strained. Likely, a correlation between the CT and strain state in the LMO/STO SLs could be envisioned. In addition, it is known that magnetic properties of, e.g., LMO 6 /SMO 4 SLs, [13] can be influenced by the epitaxy strain actuated by the chosen substrate, i.e., STO, LSAT, or LaAlO 3 (LAO). Namely, a small tensile strain in case of STO (a STO = 0.3905 nm) or an almost strain-free state for the lattice matched LSAT (a LSAT = 0.3868 nm) both promote ferromagnetism. In contrast, a compressive strain produced by the LAO substrate (a LAO = 0.3787 nm) suppresses ferromagnetic ground state. However, the development of emergent magnetic phenomena in a wide range of LMO m /SMO n compositions and layer thicknesses as well as the correlations between the lattice structure and strain state of SLs are far from being well understood. Moreover, a possibility to control CT by growth design Emergent phases at the interfaces in strongly correlated oxide heterostructures display novel properties not akin to those of constituting materials. The interfacial ferromagnetism in (LaMnO 3 ) m /(SrMnO 3 ) n (LMO) m /(SMO) n superlattices (SLs) with antiferromagnetic bulk LMO and SMO layers is believed to be a result of the interfacial charge transfer (CT). By using in situ optical ellipsometry, it is demonstrated directly that ...