Mössbauer Study of Hyperfine Field, Quadrupole Interaction, and Isomer Shift of Fe57 in FeS1.00, FeS1.05 and FeS1.07

The hyperfine structures of Fe 57 in FeS 1.00 , FeS 1.05 and FeS 1.07 have been investigated by the method of the Mössbauer absorption. The extrapolated values of the magnetic fields at the iron nuclei in FeS 1.00 , FeS 1.05 and FeS 1.07 are 328 kOe, 318 kOe and 324 kOe at 0°K respectively. The energy shifts due to the quadrupole interaction in FeS 1.05 at 290°K and 90°K have opposite sign and their ratio is -2.8. The corresponding ratio in FeS 1.07 is -2.0. This indicates that the antiferromagnetic easy axis changes by 90° through the transition temperature from the c axis, which is considered as the direction of the largest electric field gradient, onto the c plane, while direction and value of the electric field gradient remain unchanged. Observed internal magnetic fields, quadrupole coupling constants, and isomer shifts at various temperatures are given in Table 1.