Charge carriers and small-polaron migration as the origin of intrinsic dielectric anomalies in multiferroic TbMnO3 polycrystals

Autor(es)

Silveira, L. G. D. ^[1] ; Dias, G. S. ^[1] ; Cotica, L. F. ^[1] ; Eiras, J. A. ^[2] ; Garcia, D. ^[2] ; Sampaio, J. A. ^[3] ; Yokaichiya, F. ^[4] ; Santos, I. A. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Estadual Maringa, Dept Fis, BR-87020900 Maringa, Parana - Brazil

^[2] Univ Fed Sao Carlos, Dept Fis, BR-13565905 Sao Carlos, SP - Brazil

^[3] Univ Estadual Norte Fluminense, Lab Ciencias Fis, BR-28013602 Campos Dos Goytacazes, RJ - Brazil

^[4] Inst Pesquisas Energet & Nucl, Ctr Reator Pesquisa, BR-05508000 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF PHYSICS-CONDENSED MATTER; v. 25, n. 47 NOV 27 2013.
• Citações Web of Science: 9

Resumo

Temperature-dependent and frequency-dependent dielectric investigations have been performed in TbMnO3 polycrystals sintered in either oxidative or reductive atmospheres. The results revealed the occurrence of two dielectric anomalies above 100 K, which are caused by the thermal activation of charge carriers and their motion in grain cores and grain boundaries. The temperature dependence of the bulk dc conductivity was also analysed and indicates that charge carriers move between inequivalent sites according to a variable-range-hopping mechanism. Also, a strong correlation between dielectric properties and crystalline structure was observed. Furthermore, a low-temperature dielectric relaxation, commonly reported in rare-earth manganite crystals, was observed in both samples. This relaxation follows the empirical Cole-Cole model and was attributed to small-polaron tunnelling. Polaron motion was observed to be affected by the magnetic transitions, structural properties and intrinsic anisotropies in TbMnO3. It is also worth mentioning that the dielectric anomaly due to motion of charge carriers in grain boundaries is the only one of extrinsic origin, while the anomalies related to carrier motion in grain cores and small-polaron tunnelling are intrinsic to TbMnO3. (AU)

• Processo FAPESP: 08/04025-0 - Materiais multifuncionais multiferróicos nanoestruturados: síntese, propriedades, fenomenologia e aplicações
• Beneficiário: José Antonio Eiras
• Modalidade de apoio: Auxílio à Pesquisa - Temático