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Pramana

, Volume 48, Issue 6, pp 1123–1134 | Cite as

Spin state and exchange in the quasi-one-dimensional antiferromagnet KFeS2

  • Satish Kumar Tiwary
  • Sukumaran Vasudevan
Article

Abstract

We report the optical spectra and single crystal magnetic susceptibility of the one-dimensional antiferromagnet KFeS2. Measurements have been carried out to ascertain the spin state of Fe3+ and the nature of the magnetic interactions in this compound. The optical spectra and magnetic susceptibility could be consistently interpreted using aS=1/2 spin ground state for the Fe3+ ion. The features in the optical spectra have been assigned to transitions within thed-electron manifold of the Fe3+ ion, and analysed in the strong field limit of the ligand field theory. The high temperature isotropic magnetic susceptibility is typical of a low-dimensional system and exhibits a broad maximum at ∼565K. The susceptibility shows a well defined transition to a three dimensionally ordered antiferromagnetic state atT N=250 K. The intra and interchain exchange constants,J andJ′, have been evaluated from the experimental susceptibilities using the relationship between these quantities, andχ max,T max, andT N for a spin 1/2 one-dimensional chain. The values areJ=−440.71 K, andJ′=53.94 K. Using these values ofJ andJ′, the susceptibility of a spin 1/2 Heisenberg chain was calculated. A non-interacting spin wave model was used belowT N. The susceptibility in the paramagnetic region was calculated from the theoretical curves for an infiniteS=1/2 chain. The calculated susceptibility compares well with the experimental data of KFeS2. Further support for a one-dimensional spin 1/2 model comes from the fact that the calculated perpendicular susceptibility at 0K (2.75×10−4 emu/mol) evaluated considering the zero point reduction in magnetization from spin wave theory is close to the projected value (2.7×10−4 emu/mol) obtained from the experimental data.

Keywords

Low-dimensional materials magnetic ordering and exchange spin-waves 

PACS Nos

75.10 75.30 78.40 

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Copyright information

© Indian Academy of Sciences 1997

Authors and Affiliations

  • Satish Kumar Tiwary
    • 1
  • Sukumaran Vasudevan
    • 1
  1. 1.Department of Inorganic and Physical ChemistryIndian Institute of ScienceBangaloreIndia

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