Mössbauer study of antiferromagnetic FeCr2Se4

Mössbauer spectra of antiferromagnetic Fe${\mathrm{Cr}}_2$ ${\mathrm{Se}}_4$ have been taken at various temperatures ranging from 77.5-300 °K. The spectra were analyzed by diagonalizing magnetic hyperfine and quadrupole interaction matrices. The magnetic hyperfine field and quadrupole splitting at 77.5 °K are found to be 89 ± 1 kOe and -1.81 ± 0.05 mm/sec, respectively. $\theta$, $\phi$, and $\eta$ values are nearly constant throughout the temperature range up to $T_{ N}$, and are 90°, 90°, and 0.33, respectively. The quadrupole splitting changes near $T_{ N}$ by 0.12 mm/sec, which may be explained by a magnetically induced electric field gradient. The isomer shift indicates that the charge state of a Fe ion has ferrous character. The Néel temperature was determined to be (218 ± 0.5) °K.