Chemically Tailorable Frustrated Systems:Magnetic order of isostructural A2M2(C2O4)F4 (A=NH4+, Cs+) (M=Co2+, Mn2+)

This proposal forms part of an exploratory study of new mixed anion coordination compounds, in particular oxalate-fluorides, which are anticipated to have frustrated magnetic properties due to competing interactions. Two of these compounds have composition A2M2(C2O4)F4, where A =NH4 or Cs; M = Co or Mn. They have a complex crystal structure based on a 'corrugated' square metal fluoride net, bridged by oxalate anions. The NH4/Co and Cs/Mn samples are isostructural at ambient T, but the former shows a structural transiton around 100K, which apparently correlates with an abrupt change in magnetic susceptibility. In contrast, the Cs/Mn sample shows a transition to long-range magnetic order near 70 K, without a structural phase transition. The aim of this experiment is to probe the magnetic ordering of both samples, in order to correlate this with thedifferences in composition and structure