Abstract
Electric switching of non-polar bulk crystals is shown to occur when domain walls are polar in ferroelastic materials and when rough surfaces with steps on an atomic scale promote domain switching. All domains emerging from surface nuclei possess polar domain walls. The progression of domains is then driven by the interaction of the electric field with the polarity of domain boundaries. In contrast, smooth surfaces with higher activation barriers prohibit effective domain nucleation. We demonstrate the existence of an electrically driven ferroelectric hysteresis loop in a non-ferroelectric, ferroelastic bulk material.
Highlights
Electric switching of non-polar bulk crystals is shown to occur when domain walls are polar in ferroelastic materials and when rough surfaces with steps on an atomic scale promote domain switching
Ferroelastic materials are defined by their ferroelastic hysteresis[1] in analogy with ferroelectric and ferromagnetic materials and their relevant hysteresis behavior
Non-polar bulk materials like SrTiO3 and LaAlO3 show strong local dipoles inside twin walls[15,16,17,18,19,20]. These polar properties do almost cancel in complex domain patterns[21] but slight biases lead to an overall polar behavior of the material even while the bulk of the material remains strictly non-polar[22]
Summary
Electric switching of non-polar bulk crystals is shown to occur when domain walls are polar in ferroelastic materials and when rough surfaces with steps on an atomic scale promote domain switching. Non-polar bulk materials like SrTiO3 and LaAlO3 show strong local dipoles inside twin walls[15,16,17,18,19,20]. Electric fields may influence such domain structures[23,24] and the question arises whether hysteretic behavior itself can be induced by electric fields This would mean that ferroelastic materials are (weakly) ferroelectric due to polar domain boundaries. A simple answer is found when we consider simple ferroelastic needle domains These domains can be propagated and retracted by electric fields, which constitutes ferroelectricity[25] the ferroelectric, switchable polarization is very small. A more stringent test is the switchability of uniform samples In this case, the switching needs an additional, less obvious mechanism: domains with different elements of the strain tensor need to nucleate in order to switch domains. Electric fields are applied to study the evolution of domain patterns and generate a polarization hysteresis loop
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