1. Calorimetric investigation of phase transitions in the layered antiferromagnetic molecule-based material {N(n-C5H11)4[MnIIFeIII(ox)3]}∞(ox=oxalato)
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Bhattacharjee, A., Miyazaki, Y., and Sorai, M.
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ANTIFERROMAGNETISM , *LIGANDS (Chemistry) , *CALORIMETRY , *MAGNETIC properties - Abstract
Heat capacity studies of the layered molecule-based magnetic material {N(n-C5H11)4[MnIIFeIII(ox)3]}∞ (ox=oxalato) have been made in the 2–280 K range. Two distinct heat capacity anomalies were detected at 27.1 K (TN) and 226 K corresponding to magnetic and structural phase transitions, respectively, along with a hump around 23 K. The magnetic heat capacities above TN can be well represented by
S=5/2 two-dimensional antiferromagnetic Heisenberg model of a honeycomb lattice with intralayer exchange interaction J/kB=-3.3 K. Application of spin-wave theory indicated the existence of a very weak interlayer magnetic interaction below TN. The anomaly at 27.1 K is due to the antiferromagnetic transition, in conformity with the magnetic results reported earlier. The hump around 23 K might be associated with the existing uncompensated magnetic moments. The estimated magnetic entropy (33.22 J K-1 mol-1) is close to the expected magnetic entropy (R ln (6×6)=29.80 J K-1 mol-1) for the spin multiplicity of high spin MnII and FeIII ions. The heat capacity anomaly at 226 K may be assigned to a structural phase transition of order–disorder type due to increasing conformational change of the n-C5H11 chains in the organic cation. [Copyright &y& Elsevier]- Published
- 2004
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