Atomic and magnetic structures, and unconventional superexchange interactions in Sr2GaMnO5+ (0<x<0.5) and Sr2GaMn(O,F)6

Abstract The layered brownmillerite-type manganese oxide system Sr2GaMnO5+x with mixed Mn3+/ Mn4+ valence has been studied by neutron powder diffraction. The type of magnetic order is controlled by both the structure of the nonmagnetic GaO1+x buffer layer and orbital configuration of Mn. In Sr2GaMn(O,F)6 the Mn-valence can be varied while all the anion positions in the buffer layer are kept completely filled. We present the results of our studies of the crystal and magnetic structures in the end members of this family (x=0, 0.52) and for intermediate compositions (x=0.41) and Sr2GaMnO4.8F1.2 with Mn valence +3.8.