Heat capacity study of magnetoelectronic phase separation in La1-x Srx CoO3 single crystals

We present a detailed investigation of the specific heat (0.35<T<270Å) and ordinary Hall effect (300 K) in La1-x Srx CoO3 single crystals at 11 doping values in the range 0.00<x<0.30. The data reveal a considerable amount of information on the nature of the percolation transition, the crystal and electronic structures, and, most significantly, the magnetoelectronic phase inhomogeneity that has attracted such attention in this material. The observations include a discontinuity in Debye temperature accompanying the insulator-metal transition, direct evidence for the percolative nature of this transition, and a large electron mass enhancement in the metallic state, likely due to strong electron correlation effects. The various contributions to the heat capacity are shown to provide a detailed picture of the phase-separated state and its evolution with doping and are discussed in light of prior neutron-scattering and heat capacity data. This doping dependence provides strong evidence that the phase separation is restricted to a well-defined doping range, 0.04<x<0.22, in agreement with a recently proposed model.