Atomic-Scale Tuning of the Charge Distribution by Strain Engineering in Oxide Heterostructures

Abstract

Strain engineering of complex oxide heterostructures has provided routes to explore the influence of the local perturbations to the physical properties of the material. Due to the challenge of disentangling intrinsic and extrinsic effects at oxide interfaces, the combined effects of epitaxial strain and charge transfer mechanisms have been rarely studied. Here, we reveal the local charge distribution in manganite slabs by means of high-resolution electron microscopy and spectroscopy via investigating how the strain locally alters the electronic and magnetic properties of La0.5Sr0.5MnO3–La2CuO4 heterostructures. The charge rearrangement results in two different magnetic phases: an interfacial ferromagnetically reduced layer and an enhanced ferromagnetic metallic region away from the interfaces. Further, the magnitude of the charge redistribution can be controlled via epitaxial strain, which further influences the macroscopic physical properties in a way opposed to strain effects reported on single-phase films. Our work highlights the important role played by epitaxial strain in determining the spatial distribution of microscopic charge and spin interactions in manganites and provides a different perspective for engineering interface properties.

Design and Differentiation of Quantum States at Subnanometer Scale in La2CuO4−Sr2CuO4−δ Superlattices

“…The LCO layers appear brighter compared to the SCO layers due to the difference in atomic-weight between La and Sr (Z-contrast), while minor contrast variations are observed in the SCO layers. The chemical potential and crystallographic differences between orthorhombic Sr 2 CuO 3 and tetragonal LCO can result in La/Sr intermixing, as discussed later (cf. Figure ).…”

Superconductivity at Interfaces in Cuprate‐Manganite Superlattices

“…Such strong effects can even result in completely different physical properties in the strained thin film compared to the unstrained bulk material. [ 34–36 ]…”

“…Such strong effects can even result in completely different physical properties in the strained thin film compared to the unstrained bulk material. [34][35][36] The impact of these structurally distorted MnO 6 -octahedra on the electronic configuration of the manganite layers is characterized by utilizing ELNES analyses with atomic resolution (Figure 5). To gain a deeper understanding of the individual unoccupied DOS of the MnO 6 -octahedra, we divide the crystallographic unit cell of the Sr 2−x La x MnO 4 phases into first and second monolayers as shown in Figure 5a and perform ELNES analyses on raw data.…”

Extreme Enhanced Curie Temperature and Perpendicular Exchange Bias in Freestanding Ferromagnetic Superlattices

“…Interfacial effects in the strongly correlated quantum heterostructures have been demonstrated to be an important factor to induce many emergent physical phenomena, mainly as a result of the intricate coupling of multiple degrees of freedom and the delicate balance of competing orders at heterointerfaces. − The strain produced by the substrates, however, still remains to have a significant impact on the ferromagnetic properties in heterostructures or SLs . Thus, by varying the rigid substrate with different strain conditions, one can directly modify the interfacial magnetic couplings, such as interfacial magnetic phase, enhanced magnetic order temperature, and exchange bias. − In other words, the role of the epitaxial strain and interface effects on interfacial magnetic coupling in heterostructures is not yet well-understood and explored. Therefore, the freestanding ferromagnetic SLs can provide an unprecedented opportunity to study the interfacial effect on the magnetic coupling experimentally excluded the substrate clamping.…”