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Abstract
The grain size and field amplitude dependences of hysteresis loops of barium titanate ceramics have been studied in the framework of Landau theory. The Landau coefficients have been estimated from the hysteresis loops of ceramic samples with different grain sizes and compared with their size dependence predicted by Ishibashi lattice model. The same procedure has been adopted for analyzing the hysteresis loops measured at different electric field amplitudes. A correlation between the size and electric field effects has been proposed by analyzing the values of the Landau coefficients. It is considered that Landau switching occurs in an electric field-dependent confined volume due to the 90° domain walls displacements that are proportional to the applied field. Also another effects were shown to have an important contribution to the electric field dependence of second order Landau coefficient.