AVS 60th International Symposium and Exhibition
    Magnetic Interfaces and Nanostructures Monday Sessions
       Session MI+EM+MG-MoA

Paper MI+EM+MG-MoA10
A New Tool to Manipulate the Transition Metal Crystal Field: Creating Local Dipoles via Cation Ordering

Monday, October 28, 2013, 5:00 pm, Room 202 A

Session: Frontiers of Complex Oxides
Presenter: B. Nelson-Cheeseman, University of St. Thomas
Authors: B. Nelson-Cheeseman, University of St. Thomas
H. Zhou, Argonne National Laboratory
J. Hoffman, Argonne National Laboratory
P. Balchandran, Drexel University
A. Cammarata, Drexel University
J.M. Rondinelli, Drexel University
A. Bhattacharya, Argonne National Laboratory
Correspondent: Click to Email
In complex oxides, the intriguing electronic, magnetic and orbital properties often result from how the oxygen anions surround the transition metal cation. Altering this bonding geometry, and thus the transition metal crystal field, can stabilize new and exciting ground states. Here, we present a novel method to tune the positions of the oxygen anions--and, thus, the crystal field--by creating polar interfaces within a single thin film material. By using the atomic monolayer control of molecular beam epitaxy (MBE), we are able to introduce “artificial” interfaces into a thin film of LaSrNiO4--a material in which the La and Sr dopant cations are usually randomly arranged over the A-sites. Using MBE, we interleave full layers of SrO (+0) and LaO(+1) in a series of chemically equivalent LaSrNiO4 films, varying the pattern of SrO and LaO layers relative to the NiO2 layers. This technique allows us, in one material, to capitalize on the polar interface phenomena found in more traditional multi-component systems (e.g. LAO/STO). Through synchrotron surface x-ray diffraction and Coherant Bragg Rod Analysis (COBRA) performed at the Advanced Photon Source, we directly investigate the La and Sr cation order and the resulting atomic displacements throughout the film thickness for each ordering pattern. We correlate these results with theoretical calculations and transport measurements of the layered nickelate films. For a particular interface pattern, we find that the nickel-oxygen bond lengths change by as much as 10% compared to the random alloy control films. The ability to modify the bond lengths by such a significant amount, while still maintaining the overall chemical equivalency of the material, could have broad implications for re-envisioning the electronic, magnetic and orbital properties of well-known oxide materials.