Investigation of the role of morphology on the magnetic properties of Ca2Mn3O8 materialsElectronic supplementary information (ESI) available: Full details of all GSAS refinements performed on the powder X-ray diffraction data including full refinement profiles and refinement data. Additional EXAFS data fits and comparisons for the materials not shown in the main body of the text and further supporting data for the magnetic characterisation. See DOI: 10.1039/c7dt03053c

• Main Authors: Vera Stimpson, Laura J, Ramos, Silvia, Stenning, Gavin B. G, Jura, Marek, Parry, Stephen, Cibin, Giannantonio, Arnold, Donna C
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c7dt03053c

Ca 2 Mn 3 O 8 exhibits a complex layered structure comprised of Mn 3 O 8 4− layers separated by Ca 2+ ions. In contrast with the more traditional triangular delafossite layered materials the Mn 3 O 8 4− layers additionally exhibit an ordered vacancy, which forms a 'bow-tie' like arrangement of the Mn 4+ ions. We report a comprehensive study of the magnetic properties of a series of Ca 2 Mn 3 O 8 materials with different morphologies. EXAFS and XANES analysis confirm no differences in either manganese environment or oxidation state between materials. Apparent differences in magnetic order from SQUID magnetometry can be rationalised by uncompensated surface spins arising as a result of changes to the surface to volume ratio between morphologies. Furthermore, these data suggest these materials are potentially frustrated in nature, due to the triangular connectivity of Mn 4+ spins, with a simple 'spin-up/spin-down' (↑↓) antiferromagnetic model unable to explain the data collected. Ca 2 Mn 3 O 8 exhibits a complex 'bow-tie' magnetic lattice resulting in interesting magnetic behaviour.