Lattice-form dependent orbital shape and charge disproportionation in charge- and orbital-ordered manganites

Abstract

The orbital shapes and charge disproportionations at nominal Mn${}^{3+}$ and Mn${}^{4+}$ sites for the charge- and orbital-ordered phases have been studied on half-doped manganites Pr(Sr${}_{0.1}$Ca${}_{0.9}$)${}_2$Mn${}_2$O${}_7$ and Eu${}_{0.5}$Ca${}_{1.5}$MnO${}_4$ with double-layer and single-layer Mn-O networks, respectively, by means of x-ray structural analyses, in comparison with Pr${}_{0.5}$Ca${}_{0.5}$MnO${}_3$ with the pseudo cubic network. In a single-layer Eu${}_{0.5}$Ca${}_{1.5}$MnO${}_4$ system, the ($y^2-z^2$)/($z^2-x^2$)-type orbital shape is observed, while the ($3y^2-r^2$)/($3x^2-r^2$)-type orbital shape in a pseudo cubic Pr${}_{0.5}$Ca${}_{0.5}$MnO${}_3$ system. In a double-layer Pr(Sr${}_{0.1}$Ca${}_{0.9}$)${}_2$Mn${}_2$O${}_7$ system, the orbital shape is found to undergo a large change upon thermally induced rotation of orbital stripe. Furthermore, clear charge disproportionation is observed for the pseudo cubic and double-layer systems, while not in the single-layer system. These results indicate that the orbital shape and charge disproportionation are sensitive to the dimension of Mn-O network.

12 page, 5 figures, 11 tables

References in corpus (1)

• Weak charge-lattice coupling requires reinterpretation of stripes of charge order in La1-xCaxMnO3