AVS 53rd International Symposium
    Magnetic Interfaces and Nanostructures Wednesday Sessions
       Session MI-WeM

Paper MI-WeM11
Intrinsic Nanoscale Electronic Phase Separation and Simple Percolation in La1-xSrxCoO3

Wednesday, November 15, 2006, 11:20 am, Room 2006

Session: Magnetic Imaging
Presenter: J. Wu, University of Minnesota
Authors: J. Wu, University of Minnesota
J. Parker, University of Minnesota
M. Torija, University of Minnesota
C. Perrey, University of Minnesota
C.B. Carter, University of Minnesota
J. Lynn, National Institute of Standards and Technology
H. Zheng, Argonne National Laboratory
J. Mitchell, Argonne National Laboratory
C. Leighton, University of Minnesota
Correspondent: Click to Email
The doped pervoskite cobaltite La1-xSrxCoO3 has been advanced as a model system for studying magnetoelectronic phase separation. We present here a combination of chemically sensitive high-resolution TEM, SANS, and transport data that reveal interesting new features of this phase separation. The TEM data show that the material is chemically homogenous down to nm length scales, proving that the phase separation is truly intrinsic electronic phase separation. The SANS data, which were performed at several compositions below x = 0.18 (where long-range ferromagnetism (FM) sets in), reveal that the FM clusters have a maximum size of about 2-3 nm, independent of doping. This demonstrates that the percolation transition that occurs at x = 0.18 is due to an increasing density of clusters with increasing x, not an expansion of cluster size. These observations naturally explain the simple percolation observed in single crystal transport, i.e. conductivity exponents close to predicted values and a critical composition (x = 0.18) close to the expected value for the 3-D percolation limit. Comparisons to theoretical work on purely electronic phase separation provide insight into the physical mechanisms controlling the phase separation. Work supported by ACS PRF, NSF and DoE.