W0268

Dynamical Disorder in the Spin-induced Jahn-Teller Cobaltates. Despina Louca, Physics Dept., Univ. of Virginia, 382 McCormick Rd., Charlottesville, VA 22904 USA.

La_1-xSr_xCoO₃ crosses over from a ferromagnetic metal to a paramagnetic (PM) insulator through a spin transition process that induces Jahn-Teller (JT) type distortions. Locally, the atomic structure in the PM phase sensitively reflects the growth of a Jahn-Teller lattice in an undistorted low-spin matrix. The size of the JT lattice increases almost linearly with the charge concentration. Below the transition and as the charge mobility increases, a new state emerges that is the result of the change in the dynamics of the JT fluctuations. Such a dynamically fluctuating JT state could give rise to a frustrated local structure.