Dynamics of phase transitions in La1-xSrxCoO3

The unique spin transitions present in lanthanum cobaltate subject the system to variable spin-lattice coupling and to a potentially new mechanism for the insulator-metal transition. The transitions occur with increasing temperature and carrier concentration from low spin (non-magnetic) to either a high-spin or an intermediate-spin (IS) (both magnetic) configurations where the IS state is Jahn-Teller active. Earlier studies of the local structure provided strong evidence for the presence of localized lattice distortions associated with a Jahn-Teller active mode with Sr doping. Recent measurements of the dynamic structure function couple the local effects to changes in lattice dynamics with temperature and composition and provide a time-scale for the atomic fluctuations