MOSSBAUER-EFFECT STUDY OF THE MAGNETIC STATE OF IRON ATOMS IN FE-NI 36-WT-PERCENT INVAR-ALLOYS

The Fe-57 Mossbauer spectra of the Fe-Ni 36 wt.% Invar alloy at differ ent temperatures (300-530 K) have been measured. The experimental resu lts indicate that the hyperfine field distributions are characterized by dual peaks. The temperature dependence of the hyperfine field indic ates that some iron atoms may transfer from the ferromagnetic state to the antiferromagnetic one with increasing temperature, and that the v ariation of the ratio of number N-0 of the iron atoms in the antiferro magnetic state to the number N-h in the ferromagnetic state with tempe rature will obey the thermodynamic relationship.