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Ferroelectric and antiferroelectric coupling in superlattices of paraelectric perovskites at room temperature

2003; American Physical Society; Volume: 68; Issue: 2 Linguagem: Inglês

10.1103/physrevb.68.020101

1095-3795

Hans M. Christen, E. D. Specht, Sherwood S. Silliman, K. S. Harshavardhan,

Photorefractive and Nonlinear Optics

Results from dielectric and structural measurements on epitaxial ${\mathrm{SrTiO}}_{3}/{\mathrm{BaZrO}}_{3}$ superlattices reveal properties that cannot be explained simply in terms of those measured on single films of the constituent materials. For large superlattice periodicities (20/20 and 38/38 structures---i.e., samples in which each ${\mathrm{SrTiO}}_{3}$ and ${\mathrm{BaZrO}}_{3}$ layer are 20 or 38 unit cells thick, respectively), the capacitance-voltage curves indicate room-temperature ferroelectricity. For smaller periodicities (7/7 and 15/15), antiferroelectric-type behavior is observed, suggesting strong coupling between individual polar layers. This is consistent with recent second-harmonic generation results [A.Q. Jiang et al., J. Appl. Phys. 93, 1180 (2003)] of ordering in ${\mathrm{SrTiO}}_{3}/{\mathrm{BaTiO}}_{3}$ superlattices. However, both constituents of the structures investigated here are paraelectric. Strain-induced room-temperature ferroelectricity in ${\mathrm{SrTiO}}_{3}$ and distance-dependent coupling between these layers are proposed as mechanisms leading to the observed behavior.