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College Park, Maryland      June 6 - 10 , 2004

T3-A6 (5:15 PM): Spin and lattice correlations in La1-xSrxCoO3 cobaltites

S. Rosenkranz, P.J. Chupas, R. Osborn, J.F. Mitchell (Argonne National Laboratory), J.W. Lynn (NIST Center for Neutron Research), D. Louca (Virginia University)

The cobaltites La1-xSrxCoO3 show intriguing spin, lattice, and orbital properties similar to the ones observed in colossal magnetoresistive manganites. The x = 0 parent compound is a non-magnetic insulator at low temperatures, but shows evidence of spin-state transitions of the cobalt ions above 100 K from low-spin to intermediate and/or high-spin configurations. Upon doping, these systems show spin glass-like behavior with a sharp transition to ferromagnetic order at x ~ 0.2. There is a concomitant metal-insulator transition, which appears analogous to similar transitions in the phase diagram of CMR manganites. We have recently succeeded in growing large (~ 5 g), high-quality, single crystals of these compounds, which are suitable for studying in detail the spin, lattice, and orbital correlations, and their possible connection to transport properties. Our neutron and synchrotron x-ray scattering investigations of x = 0.2 doped system reveal a relatively large gap in the spin-wave excitation spectrum below, and the existence of structural distortions above Tc

This work is supported by US DOE BES-DMS W-31-109-ENG-38 and the NSF.

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