Antiferromagnetism in fcc and hcp Iron—Manganese Alloys: Mössbauer Effect

That metallic antiferromagnetism can be verified by employing the Mössbauer effect has been demonstrated for fcc FeMn alloys near the compositions of equal atomic fractions and for a hcp Fe-Mn alloy with 17% Mn. The hyperfine fields deduced from measurements of line broadening of incompletely resolved spectra give 33, 39, 43, 42, and 22 kG for 60, 50, 45, and 43% Mn in the fcc phase and 17% Mn in the hcp phase, respectively. The uncertainty is estimated at ±2.5 kG. Néel temperatures of 500°K are found for the four fcc alloys. The hcp alloy has a Néel temperature of 240°K. These values agree with resistivity and susceptibility data. In the light of this treatment of incompletely resolved spectra, a suggested reinterpretation of previous data on antiferromagnetic Cr is offered.