IMF2017

The recent progress on the high-resolution observation technique guides us towards the new research direction on domain boundary. Now we are able to measure the physical properties of domain boundaries and it turns out that they exhibit different properties from the bulk. For example, the superconductivity, high defect mobility, photovoltaic effect, unusual vortices, and ferroelectricity have been reported in many oxides. Here, we present the second harmonic generation microscope (SHGM) observation results on ferroelastic CaTiO3 single crystal. SHG is very powerful method since it is very sensitive to detect the lack of spatial inversion and time reversal. Using the confocal system with piezo-stage, we are able to construct the three dimensional image of the specimen. Our SHGM observation of CTO single crystal tells that the domain boundary in CTO shows the polar nature. A compressive uniaxial mechanical stress is applied on CTO and the change in the domain structure is observed under the polarizing microscope and SHGM. New domain boundaries appear perpendicular to the original ones under the stress. The SHG microscope observations and analyses confirm that this type of stress-induced domain boundaries are polar similar to the original ones and crystallographically prominent with the monoclinic symmetry m. The quantitative estimation of this stress-induced effect reveals that CTO is hard ferroelastic in the sense that the domain boundary movement requires a large stress. Possible application of this phenomenon is discussed.