Surface- and strain-tuning of the optical dielectric function in epitaxially grown CaMnO3

Abstract

We report a strong thickness dependence of the complex frequency-dependent optical dielectric function in epitaxial CaMnO3(001) thin films on SrTiO3(001), LaAlO3(001), and SrLaAlO4(001) substrates. A doubling of the peak value of the imaginary part of the dielectric function and spectral shifts of 0.5 eV for a given magnitude of absorption are observed. On the basis of the experimental data and first-principles density functional theory calculations of the dielectric function, its evolution with thickness from 4 to 63 nm has several regimes. In the thinnest, strain-coherent films, the response is characterized by a significant contribution from the free surface that dominates strain effects. However, at intermediate and larger thicknesses approaching the bulk-like film, strain coherence and partial strain relaxation persist and in influence the dielectric function.

7 pages text, 16 pages total, 4 figures, 1 table

References in corpus (7)

• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• Strain controlled oxygen vacancy formation and ordering in CaMnO${}_3$
• Engineering multiferroism in CaMnO${}_3$
• Incipient ferroelectricity in 2.3% tensile-strained CaMnO3 films
• General Microscopic Model of Magnetoelastic Coupling from First-Principles
• Effect of Site-disorder, Off-stoichiometry and Epitaxial Strain on the Optical Properties of Magnetoelectric Gallium Ferrite

Cited by in corpus (2)

• Strain induced magnetic transition in CaMnO${}_3$ ultra thin films
• Role of symmetry mismatch, charge transfer and low dimensionality in the magnetic order of CaMnO${}_3$/SrTiO${}_3$ ultrathin heterostructures