The recoilless absorption spectra of iron in the ternary alloys CoFeGe, CoFeSb and FeMnGe, which possess B82 type structure, reveal the existence of different ordering temperatures of moments at 2(a) and 2(d) sites. Using the Einstein model to describe the second order Doppler shift, it has been found thatΘE appropriate to the thermal motions of iron atoms at 2(a) and 2(d) sites in CoFeGe are different, which is also suggested by the temperature dependences of the relative areas of the corresponding component spectra. In CoFeSb, on the other hand, relative areas of the component spectra are independent of temperature, and give the relative distribution of iron at the inequivalent sites. A large difference in the isomer shifts of 2(a) and 2(d) site spectra indicates a larger number of d-electrons in the atomi configuration for 2(a) atoms. The isomer shift change is negative for 2(a) site nuclei and positive for 2(d) site nuclei with increase in temperature. The magnetic fields at 2(d) site nuclei in CoFeGe and CoFeSb alloys indicate that the moments of the parent atoms are not much different from the value in iron metal.
Volume 94, 2020
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