Magnetic-Field and External-Pressure Effect on Ferroelectricity in Manganites: Comparison between GdMnO${}_3$ and TbMnO${}_3$

Abstract

We have investigated dielectric properties in Mott insulators GdMnO${}_3$ and TbMnO${}_3$ under magnetic fields and external quasihydrostatic pressures. In the case of GdMnO${}_3$, thermal hysteresis for dielectric constant $\hat{I}\mu$ and discontinuous lattice distortion were observed at ferroelectric transition temperature ($T_C$), and ferroelectric spontaneous polarization was suppressed by application of external pressure. These results indicate that the ferroelectric transition in GdMnO${}_3$ is a first-order displacive-type one. On the other hand, the thermal hysteresis and discontinuous lattice striction were not observed at $T_C$ in TbMnO${}_3$. The peak of $\hat{I}\mu$ corresponding to ferroelectric transition was shifted toward higher temperatures by application of external pressure in TbMnO${}_3$. The ferroelectric transition of TbMnO${}_3$ was thought to be a second-order order-disorder-type one.

4 pages, 3 figures, RevTeX4, Proceedings of MMM 2004, appear in J. Appl. Phys