Origin of R-Dependent Dielectric Anomalies in RMnO3 with R = Y, Ho, Er, Tm, Yb and Lu.

A series of hexagonal polycrystalline RMnO3 (R = Y, Ho, Er, Tm, Lu and Yb) samples are systematically prepared, and their temperature-dependent magnetic susceptibility, specific heat and dielectric properties are measured, in order to investigate the origin of R-dependent dielectric behavior. The dielectric anomalies are found to be strongly correlated with the antiferromagnetic transitions. Both occur near the same temperatures (70∼100 K) and have a very similar R-dependency. Further analysis suggests that the origin of R-dependent dielectric anomalies in the ferroelectric phases could be the variation of strength of antiferromagnetic interaction via the change of in-plane lattice parameters. [ABSTRACT FROM AUTHOR]