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We present a 209 Bi and 17 O NMR study of the Mn electron spin correlations developed in the charge ordered state of Bi0.5Sr0.5MnO3 and Bi0.5Ca0.5MnO3. The unusually large local magnetic field 209 H loc indicates the dominant 6s 2 character of the lone electron pair of Bi 3+ -ions in both compounds, probably, responsible for the high temperature of charge ordering TCO. The observed difference in 209 H loc for Bi0.5Sr0.5MnO3 to Bi0.5Ca0.5MnO3 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 TCO 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 Pr0.5Ca0.5MnO3 and Bi0.5Sr0.5MnO3 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.

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