Eugene A. Eliseev, Sergei V. Kalinin, Albina Borisevich, Anna N. Morozovska
We demonstrate that the direct flexo-antiferroistortive coupling between the polarization gradient and the structural antiferroistortive order parameter should exist in multiferroics and has the form of Lifshitz invariant. This coupling strongly influences on the phase diagrams of the antiferrodistortive solid solutions, leading to the appearance of the incommensurate modulated phases, when the coupling strength exceeds the critical value proportional to the sum of inverse polar and structural correlation lengths, and subsequently to the antiferroelectric-like phases. This analysis provides new insight into origins of morphotropic and nanoscale phase-separated systems in complex oxides that have eluded macroscopic description.
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http://arxiv.org/abs/1301.2360
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