Structural and magnetic modulations inCaCuxMn7 − xO12

Abstract

Low temperature atomic position modulations and magnetic moment modulations are reported forCaCuxMn7 − xO12 (x = 0.0, 0.1and 0.23) using neutron powder diffraction. Both modulations are described with propagation vectors(0, 0, q) parallelto the c-axis in the hexagonal setting. The present neutron diffraction studies confirmthe quantitative model describing the atomic position modulations inCaCuxMn7 − xO12 (x = 0.0 and 0.1) as derived from synchrotron based powder x-ray diffractionstudies (Sławiński et al 2009 Acta Crystallogr. B 65 535). Neutron diffractionstudies confirm the relation between the atomic position modulation lengthLp and the magnetic modulationlength Lm = 2Lp between 50 K andthe Néel temperature TN. CaCuxMn7 − xO12 (x = 0.1 and 0.23) shows a magnetic phase transition near 50 K associated with considerable changes of themagnetic modulation length and the magnetic coherence length, similar to that observed in the parentCaMn7O12.