Cs. Kim et al., CRYSTALLOGRAPHIC AND MAGNETIC-PROPERTIES OF THE SPINEL PHASE FOR NIXFE1-XCR2S4, Journal of applied physics, 73(10), 1993, pp. 6986-6988
Ferrimagnetic NiFe1-xCr2S4 is found to crystallize with a pure spinel
structure in the composition range 0 less-than-or-equal-to x less-than
-or-equal-to 0.4. Fe-57 Mossbauer spectra of NixFe1-xCr2S4 have been t
aken at various temperatures ranging from 13 K to room temperature. An
alysis of Mossbauer spectra and x-ray crystallographic data indicate t
hat Ni ions occupy the tetrahedral site, and the lattice constant is i
n good agreement with Vegard's law. The isomer shifts indicate that th
e valence states of the Fe ions have a ferrous character. The Neel tem
perature increases linearly with Ni concentration, suggesting that the
superexchange interaction for Ni-S-Cr link is stronger than that for
Fe-S-Cr link. The anomalous reduction of the magnetic hyperfine field
below 70 K could be explained in terms of the cancellation effect betw
een mutually opposite orbital current field H(L) and the Fermi contact
field H(D). It is notable that, as the temperature decreases below th
e Neel temperature, both quadrupole shift and asymmetrical line broade
ning appear and increase with decreasing temperature, suggesting the p
resence of an electric-field gradient and accompanying relaxation effe
cts.