Correlation of chemical coordination and magnetic ordering in Sr3 YCo4 O10.5+δ (δ=0.02 and 0.26)

The crystal structure and magnetic ordering in ${\text{Sr}}_{3}{\text{YCo}}_{4}{\text{O}}_{10.5+\ensuremath{\delta}}$, $\ensuremath{\delta}=0.02$ and 0.26 compounds have been revisited in a detailed neutron diffraction study. The ordering is of $G$-type, with the magnetic Co moments being aligned along the $c$ axis of the tetragonal cells. In contrast to the previous studies, we, however, find an important peculiarity of the magnetic structures in the title compounds, namely, the magnetic moment magnitudes are different in the layers containing Co ions with different oxygen coordination. Along with the modulation of the coordination type and charge state of Co ions along the $c$ axis, the ordered magnetic moment magnitudes are varying concomitantly and thus the correlation between the charge and spin states of the Co ions has been directly observed.