The Magnetic Structure of G-type charge and orbital ordered Manganites

The hole-doped manganite phase diagram RE1-xAxMnO3 (oxidation states: RE = 3+, A = 2+) has been extensively studied over the last 40 years on account of both fundamental interest in charge, orbital and magnetic ordering, and technologically relevant properties such as colossal magnetoresistance. Despite extensive investigations, questions concerning the underlying structural and electronic ordering at key doping levels persist. This is in part due to the intrinsic electronic phase separation that occurs around x = 3/8, obfuscating the analysis of diffraction data. Recently we have had significant success in using the quadruple perovskites AMn7O12 as a prototype system to reveal novel ordered states, including an orbital order with charge disorder phase (A = Ca0.6Na0.4) and an unprecedented G-type orbital and charge ordering (A = Hg2+). However, the magnetic ordering associated with the latter has remained elusive due to phase segregation that is evident below the ordering temperature. Here we propose to investigate a lightly substituted sample Hg0.7Na0.3Mn7O12 which we have characterised carefully down to 10 K on the high-resolution powder diffractometer ID22, ESRF. Our sample displays the same electronic ordering as HgMn7O12, but without any phase separation. Our results will allow us to elucidate the magnetic ordering associated with G-type orbital ordering, adding a greater understanding of the electronically competing phases in the manganite phase diagram.