Modulation of atomic positions in CaCu x Mn7−x O12 (x ≤ 0.1)

Abstract

The modulation of atomic positions in CaCu x Mn7−x O12 (x = 0 and 0.1) was studied using synchrotron radiation powder diffraction below 250 and 220 K, respectively. The copper-rich member CaCu x Mn7−x O12 (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 CaCu x Mn7−x O12 (x = 0, 0.1 and 0.23) has been investigated. Long-range modulated magnetic ordering in CaCu x Mn7−x O12 (x = 0, 0.1 and 0.23) is observed below 90.4, 89.2 and 78.1 K. (0,0,q p) and (0,0,q m) are the propagation vectors describing the modulations of the atomic positions and the magnetic moments. For CaCu x Mn7−x O12 (x = 0 and 0.1) the magnetic modulation and atomic modulation lengths are related by a factor of 2 satisfying the relation (1 − q p) = 2(1 − q m).