Magnetic and Dielectric Properties of Tb0.5Ca0.5MnO3

概要

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The magnetic and dielectric properties of a perovskite manganite Tb0.5Ca0.5MnO3 were investigated. Magnetic measurements showed three characteristic temperatures, originating from charge ordering (${\sim}300$ K), antiferromagnetic ordering (${\sim}120$ K), and a transition to a glassy state (${\sim}50$ K). The coexistence of the charge and antiferromagnetic orderings was confirmed by powder neutron diffraction. AC dielectric measurements showed large dielectric constants larger than ${\sim}1000$ at approximately room temperature. The temperature dependence of the dielectric constant changed just below the charge-ordering temperature. From the analysis of $\tan\delta$, the activation energy for switching the directions of polar regions was calculated to be ${\sim}0.09$ eV, which is close to the activation energy of the Mn 3$d$ electron transfer. These results strongly suggest that the dielectric properties of this material are governed by the ordering and transfer of the Mn 3$d$ charges.
2007-10-30