The charge ordered state in half-doped Bi-based manganites studied by $^{17}$O and $^{209}$Bi NMR
/ Authors
A.Trokiner, S.Verkhovskii, A.Yakubovskii, K.Kumagai, S.-W.Cheong, D.Khomskii, Y.Furukawa, J.S.Ahn, A.Pogudin, V.Ogloblichev
and 3 more authors
/ Abstract
We present a 209 Bi and 17 O NMR study of the Mn electron spin correlations developed in the charge ordered state of Bi 0 . 5 Sr 0 . 5 MnO 3 and Bi 0 . 5 Ca 0 . 5 MnO 3 . The unusually large local magnetic field 209 H loc indicates the dominant 6 s 2 character of the lone electron pair of Bi 3+ -ions in both compounds, probably, responsible for the high temperature of charge ordering T CO . The observed difference in 209 H loc for Bi 0 . 5 Sr 0 . 5 MnO 3 to Bi 0 . 5 Ca 0 . 5 MnO 3 is suggested to be due to a decrease in the canting of the staggered magnetic moments of Mn 3+ -ions from adjacent ab layers. The modification of the 17 O spectra below T CO demonstrates that the NMR line due to the apical oxygens is a unique local tool to study the development of the Mn spin correlations. In the AF state the analysis of the 17 O spectrum of Pr 0 . 5 Ca 0 . 5 MnO 3 and Bi 0 . 5 Sr 0 . 5 MnO 3 points towards two different types of charge ordering in these systems: a site-centered for the first manganite and a bond-centered one for the second material.