Modulation of atomic positions in CaCuxMn7−xO12 (x ≤ 0.1)

The modulation of atomic positions in CaCuxMn7−xO12 (x = 0 and 0.1) was studied using synchrotron radiation powder diffraction below 250 and 220 K, respectively. The copper-rich member CaCuxMn7−xO12 (x = 0.23) does not show any modulation of the atomic positions at temperatures as low as 10 K. Using low-temperature neutron powder diffraction the modulation of the magnetic moments of Mn ions in CaCuxMn7−xO12 (x = 0, 0.1 and 0.23) has been investigated. Long-range modulated magnetic ordering in CaCuxMn7−xO12 (x = 0, 0.1 and 0.23) is observed below 90.4, 89.2 and 78.1 K. (0,0,qp) and (0,0,qm) are the propagation vectors describing the modulations of the atomic positions and the magnetic moments. For CaCuxMn7−xO12 (x = 0 and 0.1) the magnetic modulation and atomic modulation lengths are related by a factor of 2 satisfying the relation (1 − qp) = 2(1 − qm).