Discovery of Strange Kinetics in Bulk Material: Correlated Dipoles in CaCu3Ti4O12
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Dielectric spectroscopy of CaCu3Ti4O12 was performed spanning broad ranges of temperature (10-300K) and frequency (0.5Hz-2MHz). We attribute the permittivity step-fall to the evolution of Kirkwood-Fr\"oehlich dipole-correlations; reducing the moment-density due to anti-parallel orienting dipoles, with decreasing temperature. Unambiguous sub-Arrhenic dispersion of the associated loss-peak reveals the prime role of strange kinetics; used to describe nonlinearity-governed meso-confined/fractal systems, witnessed here for the first time in a bulk material. Effective energy-scale is seen to follow thermal evolution of the moment density, and the maidenly estimated correlation-length achieves mesoscopic scale below 100K. Temperature dependence of correlations reveals emergence of a new, parallel-dipole-orientation branch below 85K. Novel features observed define a crossover temperature window connecting the single-dipoles regime and the correlated moments. Conciling known results, we suggest a fractal-like self-similar configuration of Ca/Cu-rich sub-phases; resultant heterogeneity endowing CaCu3Ti4O12 its peculiar electrical behaviour.
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