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Calorimetric investigation of phase transitions in the layered antiferromagnetic molecule-based material {N(n-C5H11)4[MnIIFeIII(ox)3]}∞(ox=oxalato)
- Source :
-
Journal of Magnetism & Magnetic Materials . Sep2004, Vol. 280 Issue 1, p1-9. 9p. - Publication Year :
- 2004
-
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 <f>S=5/2</f> 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]
- Subjects :
- *ANTIFERROMAGNETISM
*LIGANDS (Chemistry)
*CALORIMETRY
*MAGNETIC properties
Subjects
Details
- Language :
- English
- ISSN :
- 03048853
- Volume :
- 280
- Issue :
- 1
- Database :
- Academic Search Index
- Journal :
- Journal of Magnetism & Magnetic Materials
- Publication Type :
- Academic Journal
- Accession number :
- 13956838
- Full Text :
- https://doi.org/10.1016/j.jmmm.2004.02.015