The tuning of oxalato-bridge on magnetic interaction and field-induced phase transition in Ba2Co2Cl2(C2O4)3•4H2O

The crystal structure of the oxalato-bridged compound Ba2Co2Cl2(C2O4)(3)center dot 4H(2)O has C2/c symmetry and contains two types of oxalate-bridged modes. We have investigated the magnetization behavior of the Ba2Co2Cl2(C2O4)(3)center dot 4H(2)O sample with both the static and pulsed magnetic fields. The Bleaney-Bowers fitting for the temperature dependence of magnetization shows that there are two different spin-dimers with the different intra-and inter-dimer interactions. Using the high field sweep rate of the pulsed magnetic field, magnetization measurements show four continuous phase transitions (with four different critical magnetic fields) in a smaller magnetic field range from 5.5 to 7 T, which also confirms there are two different dimers. Based on the structure analysis, the four phase transitions might result from four different magnetic exchange interactions (J(1), J(1)', J(2) and J(2)') in the two different dimers. Thus, in the design of the molecular-based magnetic materials, the oxalato-bridged and its various bridging modes can be used to mediate the magnetic interaction of the intra- and interdimers, the electronic effect between the metal ions and induce new phases.