Mössbauer study of antiferromagnetic FeCr2Se4

Abstract

M\"ossbauer spectra of antiferromagnetic Fe${\mathrm{Cr}}_{2}$${\mathrm{Se}}_{4}$ have been taken at various temperatures ranging from 77.5-300 \ifmmode^\circ\else\textdegree\fi{}K. The spectra were analyzed by diagonalizing magnetic hyperfine and quadrupole interaction matrices. The magnetic hyperfine field and quadrupole splitting at 77.5 \ifmmode^\circ\else\textdegree\fi{}K are found to be 89 \ifmmode\pm\else\textpm\fi{} 1 kOe and -1.81 \ifmmode\pm\else\textpm\fi{} 0.05 mm/sec, respectively. $\ensuremath{\theta}$, $\ensuremath{\varphi}$, and $\ensuremath{\eta}$ values are nearly constant throughout the temperature range up to ${T}_{ N}$, and are 90\ifmmode^\circ\else\textdegree\fi{}, 90\ifmmode^\circ\else\textdegree\fi{}, 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 N\'eel temperature was determined to be (218 \ifmmode\pm\else\textpm\fi{} 0.5) \ifmmode^\circ\else\textdegree\fi{}K.