Structural, electronic, and magnetic properties of nanostructured SrRuO3 epitaxial ultrathin films

Foundry User: Karin M. Rabe, Rutgers University Perovskite materials exhibit a nearly unparalleled range of electronic, magnetic, lattice-dynamical, and transport properties. Depending on their chemical composition, perovskites may exhibit insulating, superconducting, ferromagnetic, or ferroelectric behavior. The potential use of perovskite materials for novel multifunctional electronic devices has led to a strong interest in how their bulk properties are modified when they are grown as ultrathin films. Complex, artificially-designed, highly-oriented heterostructures with specific characteristics can be synthesized with atomic-level precision . Bulk-like in two lateral dimensions, these films are grown just a few nanometers thick; because of finite-size effects, the presence of interface and surfaces, and the misfit strain from epitaxial lattice-matching, it is found experimentally that the properties of many perovskite materials in thin-film form generally differ significantly from those in the bulk.

Recent studies of epitaxial thin films suggest that magnetic perovskite SrRuO3 may have novel magnetostructural properties in ultrathin-film form. By tuning the film thickness and in-plane strain through the choice of substrate, very different properties may emerge compared with bulk . In this user project with Karin Rabe of Rutgers Univeristy, we used first-principles techniques to isolate the role of epitaxial strain on the structural, electronic, magnetic properties of ultrathin SrRuO3 films, discovering that the Ru spin state can be controllably tuned with epitaxial strain. We examine the magnitude of the orthorhombic distortion in the ground state and also the effects of applying epitaxial constraints, whereby the influence of large (in the range of ±4%) in-plane strain resulting from coherent epitaxy, for both [001] and [110] oriented films, has been isolated and investigated. The overall pattern of the structural relaxations reveals coherent distortions of the oxygen octahedron network, which determine the stability of the magnetic moment on the Ru ion. The structural and magnetic parameters exhibit substantial changes, allowing us to discuss the role of symmetry and the possibility of magnetostructural tuning of SrRuO3-based thin-film structures.

Publication arising from this work: K.M. Rabe, A.T. Zayak, X. Huang, and J.B. Neaton, "Structural, electronic, and magnetic properties of SrRuO3 under epitaxial strain," Physical Review B 74, p.94104, (2006).