The magnetic semiconductor NixFe1-xCr2S4 (X = 0.985, 0,97, 0.96) has b
een investigated over the temperature range from 12 to 600 K using a M
ossbauer technique. The electronic structure of Fe ions in NiCr2S4 Was
calCUlated with the Hamiltonian incorporating free-ion term, axial an
d rhombic crystal field, spin-orbital couplings, and exchange interact
ions. The ground orbital state is separated by 9.64 \lambda\ from the
first excited state, thereby making the quadrupole splitting somewhat
insensitive to temperature. Using x-ray crystallographic data, the con
tribution of direct lattice sum to the electric-field gradient has bee
n considered. In calculating the temperature dependence of quadrupole
splitting, the axial field parameter DELTA1 = -3.0\lambda\, the rhombi
c field parameter DELTA2 = - 2.8 \lambda\, and the covalency factor al
pha2 = 0.73 in Ni0.985Fe0.015Cr2S4 were determined. Magnetic hyperfine
and quadrupole interactions in the antiferromagnetic state of Ni0.96F
e0.04Cr2S4 at 12 K have been studied, yielding the following results:
H = 147.8 kOe, 1/2e2qQ(1 + 1/3eta2)1/2 = -1.96 mm/s, theta = 66-degree
s, phi = 90-degrees, and eta = 1.0. The line broadening which suggests
the electron relaxation was observed with decreasing temperature.