title: Helical screw type magnetic structure of the multiferroic CaMn7O12 with low Cu-doping.
abstract: The modulated crystal structure and modulated magnetic ordering of the multiferroic CaCu(x)Mn(7-x)O(12) is studied by analysing neutron and synchrotron-radiation (SR) powder diffraction data with a model based on the magnetic superspace group R31'(00γ)ts. Both atomic position modulations and magnetic modulations are described with the modulation vector (0, 0, q). The magnetic ordering is a screw-type circular helix where the magnetic moments are perpendicular to the c direction. The temperature dependence of the modulation vector length and the ordered magnetic moments of Mn(3+) and Mn(4+) ions is given between T = 50 K and the Néel temperature T(N) is approximately equal to 90 K. The atomic position modulation length L(p) and the magnetic modulation length L(m) fulfil the relation L(m) = 2L(p) at all temperatures between 50 K and T(N).
authors.affiliation: Institute of Experimental Physics, University of Warsaw, Warsaw, Poland. wojciech.slawinski@fuw.edu.pl
authors.forename: W
authors.initials: W
authors.lastname: Sławiński
authors.forename: R
authors.initials: R
authors.lastname: Przeniosło
authors.forename: I
authors.initials: I
authors.lastname: Sosnowska
authors.forename: V
authors.initials: V
authors.lastname: Petříček