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

Abstract

We have investigated the magnetic hyperfine structure of iron sulfide Fe0.92S by Mössbauer spectroscopy and studied its magnetic properties. From the x-ray diffraction pattern, Fe0.92S is found to be a 3c-type superstructure of the NiAs hexagonal structure. Magnetization curve at room temperature for Fe0.92S 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 Fe7S8. 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 Néel temperature (TN) and the Debye temperature are found to be 615±1 and 238±5 K, respectively.

Identification of Mackinawite and Constraints on Its Electronic Configuration Using Mössbauer Spectroscopy

“…Wan and co-workers [22] confirmed this in a similar experiment using goethite instead of lepidocrocite, where they observed the presence of polysulfides (S 2 (-II), S n (-II)) and elemental sulfur (S 8 ) on mineral surfaces. Since mackinawite crystals grow by particle aggregation [30], incorporation of polysulfides and elemental sulfur would lead to mackinawite with a slight excess in S. A deviation from stoichiometry with less Fe than S has been shown to result in magnetic ordering [34]. A slight excess of sulfide may also explain the occurrence of this six-line pattern upon freeze drying of precipitated mackinawite.…”

Light‐Controlled Ferromagnetism in Porphyrin Functionalized Ultrathin FeS Nanosheets

“…Moreover, the temperature-dependent magnetization (M-T) curve at external magnetic field of 400 Oe discloses that magnetic anomaly associated with the phase transition from FM to AFM configuration mainly occurs at 350-370 K ( Figure S5, Supporting Information), which clues a possible spin flip under a lower external energy. [16][17][18][19] How does ferromagnetism generate in this AFM FeS material? In order to answer this question, the magnetic structure transition induced by symmetry breaking at the FeS (001) surface was calculated and shown in Figure 2b.…”

“…Through careful material screening, the troilite FeS with traditional AFM property was chosen as the optimal candidate, and was designed into the shape of ultrathin nanosheet. In the literature, [16][17][18][19] a spin flip transition between parallel to and perpendicular to the hexagonal axis (z axis, see Figure 2b) has been reported to easily occur in the troilite FeS under very small energy disturbance. On the other hand, the structural symmetry breaking plays a crucial role in determining the spin arrangement to regulate material's spin polarization.…”

Synthesis and magnetic properties of the chromium-doped iron sulfide Fe1−xCrxS single crystalline nanoplates with a NiAs crystal structure

“…This effect was recently observed in the undoped pyrrhotite Fe 1Àx S and was explained by vacancy rearrangement. 12,[24][25][26] The insertion of Cr decreases the effect of magnetization increase at 370 K, and in the sample with x = 0.15 this magnetic anomaly is not visible up to 390 K (Fig. 5a).…”