M¨ossbauer Studies on Ferrimagnetic FeCr1.7Al0.3S4

Polycrystalline Al-doped FeCr1.7Al0.3S4 has been studied with X-ray diffraction, magnetization,and M¨ossbauer spectroscopy measurements. The crystal structure was found to be a cubic spinel with a space group of Fd-3m, and the lattice constant was 10.004 °A. The magnetic susceptibility followed the Curie-Weiss law with a positive θcw = 114 K, showing a ferrimagnetic behavior. The value of the magnetization at 5 K was found to be 1.12 µB. M¨ossbauer spectra of FeCr1.7Al0.3S4were obtained at various temperatures ranging from 4.2 to 300 K. Both the magnetic hyperfine field (Hhf) and the polar angle (θ) reached their maximum values at 60 K and had similar temperature dependences. However, the azimuthal angle (ψ) remained constant at temperatures below 60 K and started increasing with temperature at temperatures above 60 K. From the M¨ossbauer spectra of FeCr1.7Al0.3S4 at 4.2 K, we obtained the following M¨ossbauer parameters: Hhf = 128 kOe, EQ = 2.42 mm/s, θ = 20.0。, ' = 0.0。, η= 0.8, and R = 2.8. The isomer shift of FeCr1.7Al0.3S4 at 4.2K was 0.83 mm/s relative to the Fe metal, which is consistent with the Fe2+ valence state.