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An amine‐templated 2D coordination polymer of Co II with the formula {[EDAH 2 ][Co 2 F 2 (SO 4 ) 2 (H 2 O) 2 ]} n ( 1 ) (EDA = ethylenediamine), has been synthesised and structurally characterised. It consists of a 1D chain bridged by F – ions, which are interconnected by SO 4 2– tetrahedra forming a 2D [Co 2 F 2 (SO 4 ) 2 (H 2 O) 2 ] n 2– corrugated sheet. The diprotonated cation [EDAH 2 ] is intercalated between the sheets. Temperature‐dependent magnetic measurements reveal the presence of spin‐canted antiferromagnetism and hard‐magnet‐like behaviour with large a magnetic hysteresis with a coercive field ( H c ) of 16.2 kOe and a remnant magnetisation ( M R ) of 1.64 μ B . The coordinated water molecules in 1 can be removed by heating at 250 °C under vacuum to obtain the dehydrated phase {[EDAH 2 ][Co 2 F 2 (SO 4 ) 2 ]} n ( 1′ ), which – upon exposure to water vapour for 24 h – gave the monoaqua compound, {[EDAH 2 ][Co 2 F 2 (SO 4 ) 2 (H 2 O)]} n ( 1″ ). This dehydration/rehydration process is accompanied by a structural transformation and a magnetic phase transition between the spin‐canted antiferromagnetic state of the hydrated phase to the antiferromagnetic state of the dehydrated phase.
Room-temperature ferromagnetism is exhibited by nanoparticles of a variety of inorganic materials although they are intrinsically non-magnetic. Typical of such nanomaterials are the oxides, CeO2, TiO2, Al2O3, and MgO. Nanoparticles of nitrides such as GaN and chalcogenides such as CdS and CdSe also exhibit ferromagnetism. Ferromagnetism of the nanoparticles is confined to the surface. This phenomenon has been utilized to render the classic ferroelectric BaTiO3 to be multiferroic wherein surface ferromagnetism coexists with bulk ferroelectricity. Interestingly, nanoparticles of superconducting YBa2Cu3O7 show surface ferromagnetism. It is possible that surface ferromagnetism of inorganic nanoparticles can be usefully exploited.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
