title: Crystal and magnetic structures of afeIIFeIII(C2O4)3 (A = organic cation): two-dimensional honeycomb ferrimagnets.
abstract: Ferrimagnetic tris-oxalato-ferrate(II,III) salts with general formula AFeIIFeIII(C2O4)3 (A = quaternary ammonium, phosphonium) all crystallise in two-dimensional hexagonal honeycomb lattices but while some show conventional Néel type Q magnetisation at low temperature others show negative Néet type N magnetisation below a compensation temperature Tcomp. The compounds having negative magnetisation show a discontinuity in the magnetisation at a temperature between Tcomp and Tc suggesting a magneto-strictive transition. For the type Q compounds, hysteresis and frequency dependent AC susceptibility show that the low temperature magnetic state is glassy, either because of frustration of random anisotropy domains below a blocking temperature, or imbalance in the fractions of FeII and FeIII.
authors.affiliation: Day Faraday Research Laboratory, The Royal Institution of Great Britain, London, UK.
authors.forename: S G
authors.initials: SG
authors.lastname: Carling
authors.forename: P
authors.initials: P
authors.lastname: Day
authors.forename: C J
authors.initials: CJ
authors.lastname: Nuttall
mesh_terms: D016880:Anisotropy; D002412:Cations; D018360:Crystallography, X-Ray; D007501:Iron / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008280:Magnetics; D008958:Models, Molecular; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013053:Spectrophotometry; D013696:Temperature
chemical_list: D002412:Cations; D000644:Quaternary Ammonium Compounds; C017311:ferrate ion; D007501:Iron