Mössbauer study of magnetic structure of cation-deficient iron sulfide Fe0.92S

Abstract

We have investigated the magnetic hyperfine structure of iron sulfide Fe0.92 S by Mössbauer spectroscopy and studied its magnetic properties. From the x-ray diffraction pattern, Fe0.92 S is found to be a 3c -type superstructure of the NiAs hexagonal structure. Magnetization curve at room temperature for Fe0.92 S showed a ferromagnetic behavior unlike that for antiferromagnetic FeS. A peak type anomaly is observed in zero-field-cooled magnetization curve under 100 Oe. Mössbauer spectra were taken at various temperatures ranging from 4.2 to 615 K. The spectra consist of three-component subspectra arising from three magnetically nonequivalent sites in the 3c superstructure. The magnetic hyperfine fields of the three A -, B -, and C -sites at 4.2 K are found to be 328, 277, and 246 kOe, respectively. These values are in the ratio of 18:15:14, which is close to the ratio of the magnitudes of magnetic hyperfine field in 18, 14, and 13 interplanar superexchange links (Fe-S-Fe) of A -, B -, and C -sites in Fe7 S8. The absorption intensity for A -, B -, and C -sites changes substantially over the temperature range from 570 K, suggesting that a vacancy rearrangement is taking place. Isomer shifts indicate Fe2+ states for all three sites. The Ńel temperature (TN) and the Debye temperature are found to be 615±1 and 238±5 K, respectively. © 2009 American Institute of Physics.