Abstract
Transition metal functional oxides, e.g., perovskite manganites, with strong electron, spin and lattice correlations, are well-known for different phase transitions and field-induced colossal effects at the phase transition. Recently, the interfaces between dissimilar perovskites were shown to be a promising concept for the search of emerging phases with novel functionalities. We demonstrate that the properties of manganite films are effectively controlled by low dimensional emerging phases at intrinsic and extrinsic interfaces and appeared as a result of symmetry breaking. The examples include correlated Jahn–Teller polarons in the phase-separated (La1−yPry)0.7Ca0.3MnO3, electron-rich Jahn–Teller-distorted surface or “dead” layer in La0.7Sr0.3MnO3, electric-field-induced healing of “dead” layer as an origin of resistance switching effect, and high-TC ferromagnetic emerging phase at the SrMnO3/LaMnO3 interface in superlattices. These 2D polaronic phases with short-range electron, spin, and lattice reconstructions could be extremely sensitive to external fields, thus, providing a rational explanation of colossal effects in perovskite manganites.
Highlights
Complex transition metal oxides with perovskite structure possess strong electronic correlations and display coupled phase transitions, caused by the interplay of charge, spin, and lattice degrees of freedom
The reflection high-energy electron diffraction (RHEED) technique can operate at very low pO2 < 1 mbar in pulsed laser deposition (PLD) and molecular beam epitaxy (MBE) setups
We found the magnetism in SLs depends strongly on the thickness of the constituting SMO and LMO layers: SLs with very thin layers (n = 1,2) behave similar to a homogeneous La0.7 Sr0.3 MnO3 (LSMO) film and for n > 3 an inhomogeneous AFM/FM behavior was observed
Summary
Complex transition metal oxides with perovskite structure possess strong electronic correlations and display coupled phase transitions, caused by the interplay of charge, spin, and lattice degrees of freedom. A rich diversity of functionalities based on the involved charge, spin, and lattice degrees of freedom is the hallmark of strongly correlated oxides, called functional oxides They possess technologically important properties, such as (a) high-TC superconductivity, e.g., YBa2 Cu3 O7−δ (YBCO) with transition temperature, TC ~90 K; (b) ferroelectricity, e.g., Pb(Zr,Ti)O3 (PZT), with high remnant electrical polarization, p~100 μC/cm , and high Curie temperature, TC ~500 K; (c) a half-metallic ferromagnetism in doped manganites, e.g., (La,Sr)MnO3 , with relatively high TC = 370 K; and (d) multiferroic behavior in BiFeO3 with coexisting magnetic (G-type AFM) and ferroelectric order parameters at room temperature [17]. Of electrically highly isolated “dead layer” at the La0.7 Sr0.3 MnO3 (LSMO) surface and formation of the embedded conducting layers, which allow a robust multi-state memristive functionality
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