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

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 Fe a ÷ and the nature of the magnetic interactions in this compound. The optical spectra and magnetic susceptibility could be consistently interpreted using a S = ½ spin ground state for the Fe 3 ÷ ion. The features in the optical spectra have been assigned to transitions within the d-electron manifold of the Fe 3 ÷ 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 ~ 565 K. The susceptibility shows a well defined transition to a three dimensionally ordered antiferromagnetic state at T N = 250 K. The intra and interchain exchange constants, J and J', have been evaluated from the experimental susceptibilities using the relationship between these quantities, and X,~ax, T~,x, and Ts for a spin ½ one-dimensional chain. The values are J = -440.71 K, and J' = 53"94 K. Using these values of J and J', the susceptibility of a spin ½ Heisenberg chain was calculated. A non-interacting spin wave model was used below T s. The susceptibility in the paramagnetic region was calculated from the theoretical curves for an J infinite S = ~ chain. The calculated susceptibility compares well with the experimental data of KFeS 2. Further support for a one-dimensional spin ½ model comes from the fact that the calculated perpendicular susceptibility at OK (2.75 × 10-4emu/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.

Magnetic and transport properties, and electronic structure of the layered chalcogenide AgCrSe2

“…We find that the temperature dependence of the susceptibility is well described using a model that involves ferromagnetic coupling within the 2D triangular lattice of Cr III as described by the hightemperature series expansion (HTSE) of the Heisenberg X-Y ferromagnet [13], in conjunction with a mean-field antiferromagnetic inter-layer coupling. This scheme has been successfully applied to other layered magnetic systems [14,15].…”

Density Functional Theory Approach to the Vibrational Properties and Magnetic Specific Heat of the Covalent Chain Antiferromagnet KFeS2

“…KFeS 2 is the most extensively investigated compound of this family. Nevertheless, so far, no consensus has been reached on the magnetic ground state of this compound, and the magnetic moment values presented in the literature are different from each other [4][5][6][7]. Several investigations argue that the spin state of the iron ions in this compound is low, S = 1/2 [4,5].…”

“…Nevertheless, so far, no consensus has been reached on the magnetic ground state of this compound, and the magnetic moment values presented in the literature are different from each other [4][5][6][7]. Several investigations argue that the spin state of the iron ions in this compound is low, S = 1/2 [4,5]. Therefore, in [6], it was noticed that the spin-1/2 one-dimensional Heisenberg model provides a good fit for the temperature dependence of the susceptibility of KFeS 2 .…”