科研之友
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摘要
The hybrid improper ferroelectricity (HIF) has been proposed as a promising way to create multiferroic materials with strong magnetoelectric coupling by the first-principle calculation, and the experimental evidences of HIF in Ruddlesden-Poper Ca-3(Ti1-xMnx)(2)O-7 (x = 0, 0.05, 0.1, and 0.15) ceramics have been shown in the present work. The room temperature ferroelectric hysteresis loops are observed in these ceramics, and a polar orthorhombic structure with two oxygen tilting modes has been confirmed by the X-ray powder diffraction. A first-order phase transition around 1100K in Ca3Ti2O7 was evidenced, and the temperatures of phase transitions decrease linearly with increasing of the contents of Mn4+ ions. Based on the result of first-principle calculations, the polarization should be reversed by switching through the mediated Amam phase in Ca3Ti2O7 ceramics.
