Transport, magnetic, and magnetotransport properties of Ba3−xRxTa5O15(R

Barium tantalate with a tetragonal tungsten bronze structure, ${\mathrm{Ba}}_{3}{\mathrm{Ta}}_{5}{\mathrm{O}}_{15}$, and compounds where Ba is partly substituted by various rare earths ($R$), ${\mathrm{Ba}}_{3\ensuremath{-}x}{R}_{x}{\mathrm{Ta}}_{5}{\mathrm{O}}_{15}$, were synthesized as single crystals, and their transport, magnetic, and magnetotransport properties were investigated. It was found that the compounds with Eu substitution show a relatively large negative magnetoresistance arising from the interaction between the conduction electrons in the Ta $5d$ orbital and the localized spins in the Eu $4f$ orbital.