CoMn2O4 spinel from a MOF: synthesis, structure and magnetic studies

Abstract

A hydrothermal reaction of Mn(OAc)2·4H2O, Co(OAc)2·4H2O and 1,2,4 benzenetricarboxylic acid at 220 °C for 24 h gives rise to a mixed metal MOF compound, [CoMn2{C6H3(COO)3}2], I. The structure is formed by the connectivity between octahedral CoO6 and trigonal prism MnO6 units connected through their vertices forming a Kagome layer, which are pillared by the trimellitate. Magnetic susceptibility studies on the MOF compound indicate a canted anti-ferromagnetic behavior, due to the large antisymmetric DM interaction between the M2+ ions (M = Mn, Co). Thermal decomposition studies indicate that the MOF compound forms a tetragonal mixed-metal spinel phase, CoMn2O4, with particle sizes in the nano regime at 400 °C. The particle size of the CoMn2O4 can be controlled by varying the decomposition temperature of the parent MOF compound. Magnetic studies of the CoMn2O4 compound suggests that the coercivity and the ferrimagnetic ordering temperatures are dependent on the particle size.